├── .gitignore ├── LICENSE ├── build.gradle ├── gradle.properties ├── gradlew ├── gradlew.bat └── src ├── main └── kotlin │ └── com │ └── fernandocejas │ └── crackinginterview │ ├── Main.kt │ ├── array │ └── ArrayProblems.kt │ ├── complexity │ └── BigO.kt │ ├── list │ ├── LinkedList.kt │ └── LinkedListProblems.kt │ ├── recursion │ └── RecursionProblems.kt │ ├── string │ └── StringProblems.kt │ ├── tree │ ├── Node.kt │ ├── Sample.kt │ └── TreeProblems.kt │ └── util │ └── Performance.kt └── test └── kotlin └── com └── fernandocejas └── crackinginterview ├── array └── ArrayProblemsTest.kt ├── list ├── LinkedListProblemsTest.kt └── MyLinkedListProblemsTest.kt ├── recursion └── RecursionProblemsTest.kt ├── string └── StringProblemsTest.kt └── tree └── TreeProblemsTest.kt /.gitignore: -------------------------------------------------------------------------------- 1 | # Windows thumbnail db 2 | Thumbs.db 3 | 4 | # OSX files 5 | .DS_Store 6 | 7 | # built application files 8 | *.apk 9 | *.ap_ 10 | 11 | # files for the dex VM 12 | *.dex 13 | 14 | # Java class files 15 | *.class 16 | 17 | # generated files 18 | bin/ 19 | gen/ 20 | build/ 21 | 22 | # Local configuration file (sdk path, etc) 23 | local.properties 24 | 25 | # Eclipse project files 26 | .classpath 27 | .project 28 | 29 | # Intellij 30 | .idea 31 | .gradle 32 | gradle 33 | /*/local.properties 34 | /*/out 35 | /*/*/build 36 | build 37 | /*/*/production 38 | *.iml 39 | *.iws 40 | *.ipr 41 | *~ 42 | *.swp 43 | out 44 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script. 31 | DEFAULT_JVM_OPTS="" 32 | 33 | # Use the maximum available, or set MAX_FD != -1 to use that value. 34 | MAX_FD="maximum" 35 | 36 | warn () { 37 | echo "$*" 38 | } 39 | 40 | die () { 41 | echo 42 | echo "$*" 43 | echo 44 | exit 1 45 | } 46 | 47 | # OS specific support (must be 'true' or 'false'). 48 | cygwin=false 49 | msys=false 50 | darwin=false 51 | nonstop=false 52 | case "`uname`" in 53 | CYGWIN* ) 54 | cygwin=true 55 | ;; 56 | Darwin* ) 57 | darwin=true 58 | ;; 59 | MINGW* ) 60 | msys=true 61 | ;; 62 | NONSTOP* ) 63 | nonstop=true 64 | ;; 65 | esac 66 | 67 | CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar 68 | 69 | # Determine the Java command to use to start the JVM. 70 | if [ -n "$JAVA_HOME" ] ; then 71 | if [ -x "$JAVA_HOME/jre/sh/java" ] ; then 72 | # IBM's JDK on AIX uses strange locations for the executables 73 | JAVACMD="$JAVA_HOME/jre/sh/java" 74 | else 75 | JAVACMD="$JAVA_HOME/bin/java" 76 | fi 77 | if [ ! -x "$JAVACMD" ] ; then 78 | die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME 79 | 80 | Please set the JAVA_HOME variable in your environment to match the 81 | location of your Java installation." 82 | fi 83 | else 84 | JAVACMD="java" 85 | which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 86 | 87 | Please set the JAVA_HOME variable in your environment to match the 88 | location of your Java installation." 89 | fi 90 | 91 | # Increase the maximum file descriptors if we can. 92 | if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then 93 | MAX_FD_LIMIT=`ulimit -H -n` 94 | if [ $? -eq 0 ] ; then 95 | if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then 96 | MAX_FD="$MAX_FD_LIMIT" 97 | fi 98 | ulimit -n $MAX_FD 99 | if [ $? -ne 0 ] ; then 100 | warn "Could not set maximum file descriptor limit: $MAX_FD" 101 | fi 102 | else 103 | warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT" 104 | fi 105 | fi 106 | 107 | # For Darwin, add options to specify how the application appears in the dock 108 | if $darwin; then 109 | GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\"" 110 | fi 111 | 112 | # For Cygwin, switch paths to Windows format before running java 113 | if $cygwin ; then 114 | APP_HOME=`cygpath --path --mixed "$APP_HOME"` 115 | CLASSPATH=`cygpath --path --mixed "$CLASSPATH"` 116 | JAVACMD=`cygpath --unix "$JAVACMD"` 117 | 118 | # We build the pattern for arguments to be converted via cygpath 119 | ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null` 120 | SEP="" 121 | for dir in $ROOTDIRSRAW ; do 122 | ROOTDIRS="$ROOTDIRS$SEP$dir" 123 | SEP="|" 124 | done 125 | OURCYGPATTERN="(^($ROOTDIRS))" 126 | # Add a user-defined pattern to the cygpath arguments 127 | if [ "$GRADLE_CYGPATTERN" != "" ] ; then 128 | OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)" 129 | fi 130 | # Now convert the arguments - kludge to limit ourselves to /bin/sh 131 | i=0 132 | for arg in "$@" ; do 133 | CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -` 134 | CHECK2=`echo "$arg"|egrep -c "^-"` ### Determine if an option 135 | 136 | if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then ### Added a condition 137 | eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"` 138 | else 139 | eval `echo args$i`="\"$arg\"" 140 | fi 141 | i=$((i+1)) 142 | done 143 | case $i in 144 | (0) set -- ;; 145 | (1) set -- "$args0" ;; 146 | (2) set -- "$args0" "$args1" ;; 147 | (3) set -- "$args0" "$args1" "$args2" ;; 148 | (4) set -- "$args0" "$args1" "$args2" "$args3" ;; 149 | (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;; 150 | (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;; 151 | (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;; 152 | (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;; 153 | (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;; 154 | esac 155 | fi 156 | 157 | # Escape application args 158 | save () { 159 | for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done 160 | echo " " 161 | } 162 | APP_ARGS=$(save "$@") 163 | 164 | # Collect all arguments for the java command, following the shell quoting and substitution rules 165 | eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS" 166 | 167 | # by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong 168 | if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then 169 | cd "$(dirname "$0")" 170 | fi 171 | 172 | exec "$JAVACMD" "$@" 173 | -------------------------------------------------------------------------------- /gradlew.bat: -------------------------------------------------------------------------------- 1 | @if "%DEBUG%" == "" @echo off 2 | @rem ########################################################################## 3 | @rem 4 | @rem Gradle startup script for Windows 5 | @rem 6 | @rem ########################################################################## 7 | 8 | @rem Set local scope for the variables with windows NT shell 9 | if "%OS%"=="Windows_NT" setlocal 10 | 11 | set DIRNAME=%~dp0 12 | if "%DIRNAME%" == "" set DIRNAME=. 13 | set APP_BASE_NAME=%~n0 14 | set APP_HOME=%DIRNAME% 15 | 16 | @rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script. 17 | set DEFAULT_JVM_OPTS= 18 | 19 | @rem Find java.exe 20 | if defined JAVA_HOME goto findJavaFromJavaHome 21 | 22 | set JAVA_EXE=java.exe 23 | %JAVA_EXE% -version >NUL 2>&1 24 | if "%ERRORLEVEL%" == "0" goto init 25 | 26 | echo. 27 | echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 28 | echo. 29 | echo Please set the JAVA_HOME variable in your environment to match the 30 | echo location of your Java installation. 31 | 32 | goto fail 33 | 34 | :findJavaFromJavaHome 35 | set JAVA_HOME=%JAVA_HOME:"=% 36 | set JAVA_EXE=%JAVA_HOME%/bin/java.exe 37 | 38 | if exist "%JAVA_EXE%" goto init 39 | 40 | echo. 41 | echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 42 | echo. 43 | echo Please set the JAVA_HOME variable in your environment to match the 44 | echo location of your Java installation. 45 | 46 | goto fail 47 | 48 | :init 49 | @rem Get command-line arguments, handling Windows variants 50 | 51 | if not "%OS%" == "Windows_NT" goto win9xME_args 52 | 53 | :win9xME_args 54 | @rem Slurp the command line arguments. 55 | set CMD_LINE_ARGS= 56 | set _SKIP=2 57 | 58 | :win9xME_args_slurp 59 | if "x%~1" == "x" goto execute 60 | 61 | set CMD_LINE_ARGS=%* 62 | 63 | :execute 64 | @rem Setup the command line 65 | 66 | set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar 67 | 68 | @rem Execute Gradle 69 | "%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS% 70 | 71 | :end 72 | @rem End local scope for the variables with windows NT shell 73 | if "%ERRORLEVEL%"=="0" goto mainEnd 74 | 75 | :fail 76 | rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of 77 | rem the _cmd.exe /c_ return code! 78 | if not "" == "%GRADLE_EXIT_CONSOLE%" exit 1 79 | exit /b 1 80 | 81 | :mainEnd 82 | if "%OS%"=="Windows_NT" endlocal 83 | 84 | :omega 85 | -------------------------------------------------------------------------------- /src/main/kotlin/com/fernandocejas/crackinginterview/Main.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview 2 | 3 | fun main(args: Array) { 4 | println("-------------------------------------------") 5 | println("Cracking the Engineer Interview with Kotlin!") 6 | println("Check the source code for the problems") 7 | println("-------------------------------------------") 8 | println("Fernando Cejas") 9 | println("github.com/android10") 10 | println("twitter.com/fernando_cejas") 11 | println("-------------------------------------------") 12 | } -------------------------------------------------------------------------------- /src/main/kotlin/com/fernandocejas/crackinginterview/array/ArrayProblems.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.array 2 | 3 | import kotlin.Array 4 | 5 | /** 6 | * An array is the most fundamental data structure, which stores elements at a contiguous 7 | * memory location. The key benefit of an array data structure is that it offers fast O(1) 8 | * search if you know the index, but adding and removing an element from an array is slow 9 | * because you cannot change the size of the array once it’s created. 10 | * 11 | * In order to create a shorter or longer array, you need to create a new array and copy 12 | * all elements from old to new. 13 | */ 14 | class ArrayProblems { 15 | 16 | /** 17 | * PROBLEM: 18 | * How do you find the duplicate number on a given integer array? 19 | * 20 | * SOLUTION: 21 | * Brute force -> quadratic -> O(n2) 22 | */ 23 | fun findDuplicateBruteForce(array: Array): Int { 24 | for (i in array.indices) { 25 | for (j in array.indices) { 26 | if (i == j) continue 27 | if (array[i] == array[j]) return array[i] 28 | } 29 | } 30 | return -1 31 | } 32 | 33 | /** 34 | * PROBLEM: 35 | * How do you find the duplicate number on a given integer array? 36 | * 37 | * SOLUTION: 38 | * Better solution -> linear -> O(n) 39 | */ 40 | fun findDuplicateBetter(array: Array): Int { 41 | val sortedArray = array.sortedArray() 42 | for (i in 0..sortedArray.size - 2) { 43 | if (sortedArray[i] == sortedArray[i+1]) return sortedArray[i] 44 | } 45 | return -1 46 | } 47 | 48 | /** 49 | * PROBLEM: 50 | * How do you find the duplicate numbers on a given integer array? 51 | * 52 | * SOLUTION: 53 | * Linear -> O(n) 54 | */ 55 | fun removeDuplicatesUsingSet(array: Array): Array = 56 | array.toHashSet().toTypedArray() 57 | 58 | /** 59 | * PROBLEM: 60 | * How do you find the duplicate numbers on a given integer array? 61 | * 62 | * SOLUTION: 63 | * Linear -> O(n) 64 | */ 65 | fun removeDuplicates(array: Array): Array { 66 | val set: MutableSet = HashSet() 67 | repeat(array.size) { set.add(array[it]) } 68 | return set.toTypedArray() 69 | } 70 | 71 | /** 72 | * PROBLEM: 73 | * How do you reverse an array in place? 74 | * 75 | * SOLUTION: 76 | * O(n/2) 77 | */ 78 | fun reverseKotlin(array: Array) = array.reversedArray() 79 | 80 | /** 81 | * PROBLEM: 82 | * How do you reverse an array in place? 83 | * 84 | * SOLUTION: 85 | * O(n/2) 86 | */ 87 | fun reverse(array: Array): Array { 88 | var reverseIndex = array.size - 1 89 | for (i in array.indices) { 90 | if (i >= reverseIndex) break 91 | 92 | val tempValue = array[i] 93 | array[i] = array[reverseIndex] 94 | array[reverseIndex] = tempValue 95 | reverseIndex-- 96 | } 97 | return array 98 | } 99 | } -------------------------------------------------------------------------------- /src/main/kotlin/com/fernandocejas/crackinginterview/complexity/BigO.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.complexity 2 | 3 | /** 4 | * Big O notation is used in Computer Science to describe the performance or complexity 5 | * of an algorithm. Big O specifically describes the worst-case scenario, and can be 6 | * used to describe the execution time required or the space used (e.g. in memory or on disk) 7 | * by an algorithm. 8 | * 9 | * With Big O Notation we express the runtime in terms of : 10 | * 11 | * 1 - HOW QUICKLY THE RUNTIME GROWS — 12 | *  Being that it is difficult to determine the exact runtime of an algorithm. 13 | * It depends on the speed of the computer processor. So instead of talking about 14 | * the runtime directly, we use Big O Notation to talk about how quickly the runtime grows. 15 | * 16 | * 2 - RELATIVE TO THE INPUT — 17 | *  If we were measuring our runtime directly, we could express our speed in seconds and minutes. 18 | * Since we are measuring how quickly our runtime grows, we need to express our speed in terms 19 | * of something else. With Big O Notation, we use the size of the input, which we call “n”. 20 | * So we can say things like the runtime grows “on the order of the size of the input” (O(n)) 21 | * or “on the order of the square of the size of the input” (O(n²)). 22 | * 23 | * 3 - AS THE INPUT GETS LARGER — 24 | *  Our algorithm may have steps that seem expensive when n is small but are eclipsed eventually 25 | * by other steps as n gets larger. For Big O Notation analysis, we care more about the stuff 26 | * that grows fastest as the input grows, because everything else is quickly eclipsed as n 27 | * gets very large. 28 | */ 29 | class BigO { 30 | 31 | /** 32 | * CONSTANT: O(1) describes an algorithm that will always execute in the same time 33 | * (or space) regardless of the size of the input data set. 34 | */ 35 | fun firstElement(elements: Array) = elements.firstOrNull() 36 | 37 | /** 38 | * LINEAR: O(N) describes an algorithm whose performance will grow linearly and in 39 | * direct proportion to the size of the input data set. 40 | */ 41 | fun constainsValue(elements: Array, search: String): Boolean { 42 | elements.forEach { if (it == search) return true } 43 | return false 44 | } 45 | 46 | /** 47 | * QUADRATIC: O(N2) represents an algorithm whose performance is directly proportional to 48 | * the square of the size of the input data set. This is common with algorithms 49 | * that involve nested iterations over the data set. 50 | * Deeper nested iterations will result in O(N3), O(N4) etc. 51 | */ 52 | fun containsDuplicates(elements: List): Boolean { 53 | for (i in elements.indices) { 54 | for (j in elements.indices) { 55 | if (i != j) continue 56 | if (elements[i] == elements[j]) return true 57 | } 58 | } 59 | return false 60 | } 61 | 62 | /** 63 | * O(2N) denotes an algorithm whose growth doubles with each addition to the input 64 | * data set. The growth curve of an O(2N) function is exponential - starting off 65 | * very shallow, then rising meteorically. 66 | * 67 | * @number: the nth number in the Fibonacci sequence. 68 | */ 69 | fun fibonacci(number: Int): Int { 70 | if (number <= 1) return number 71 | return fibonacci(number - 1) + fibonacci(number - 2) 72 | } 73 | } -------------------------------------------------------------------------------- /src/main/kotlin/com/fernandocejas/crackinginterview/list/LinkedList.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.list 2 | 3 | class LinkedList { 4 | 5 | private var numberOfElements = 0 6 | private var head: Node? = null 7 | 8 | fun add(element: T) { 9 | numberOfElements++ 10 | TODO() 11 | } 12 | 13 | fun add(element: T, position: Int): Unit = TODO() 14 | 15 | fun remove(position: Int): Unit = TODO() 16 | 17 | fun get(position: Int): T = TODO() 18 | 19 | fun size(): Int = numberOfElements 20 | 21 | fun isEmpty() = numberOfElements == 0 22 | 23 | private inner class Node(val data: T) { 24 | fun next(): Node? = null 25 | } 26 | } 27 | -------------------------------------------------------------------------------- /src/main/kotlin/com/fernandocejas/crackinginterview/list/LinkedListProblems.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.list 2 | 3 | import java.util.LinkedList 4 | 5 | /** 6 | * A linked list is another common data structure that complements the array data structure. 7 | * Similar to the array, it is also a linear data structure and stores elements in a linear fashion. 8 | * 9 | * However, unlike the array, it does not store them in contiguous locations; instead, they 10 | * are scattered everywhere in memory, which is connected to each other using nodes. 11 | * 12 | * A linked list is nothing but a list of nodes where each node contains the value stored and 13 | * the address of the next node. 14 | * 15 | * Because of this structure, it’s easy to add and remove elements in a linked list, as you just 16 | * need to change the link instead of creating the array, but the search is difficult and often 17 | * requires O(n) time to find an element in the singly linked list. 18 | * 19 | * It also comes in varieties like a singly linked list, which allows you to traverse in one 20 | * direction (forward or reverse); a doubly linked list, which allows you to traverse in both 21 | * directions (forward and backward); and finally, the circular linked list, which forms a circle. 22 | * 23 | * In order to solve linked list-based questions, a good knowledge of recursion is important, 24 | * because a linked list is a recursive data structure. 25 | * 26 | * If you take one node from a linked list, the remaining data structure is still a linked list, 27 | * and because of that, many linked list problems have simpler recursive solutions than 28 | * iterative ones. 29 | */ 30 | class LinkedListProblems { 31 | 32 | /** 33 | * PROBLEM: 34 | * How do you find the middle element of a singly linked list in one pass? 35 | * 36 | * SOLUTION: 37 | * Linear -> O(n) 38 | */ 39 | fun findMiddleElement(list: LinkedList): T { 40 | val listSize = list.size 41 | val middle = when (listSize.rem(2)) { 42 | 0 -> listSize / 2 43 | else -> (listSize / 2) + 1 44 | } 45 | return list[middle] 46 | } 47 | } -------------------------------------------------------------------------------- /src/main/kotlin/com/fernandocejas/crackinginterview/recursion/RecursionProblems.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.recursion 2 | 3 | /** 4 | * RecursionProblems is a computer programming technique involving the use of a procedure, 5 | * subroutine, function, or algorithm that calls itself in a step having a termination 6 | * condition so that successive repetitions are processed up to the critical step where 7 | * the condition is met at which time the rest of each repetition is processed from the 8 | * last one called to the first. 9 | */ 10 | class RecursionProblems { 11 | 12 | /** 13 | * The factorial function, often denoted as n!, describes the operation of multiplying 14 | * a number by all the positive integers smaller than it. 15 | * For example, 5! = 5*4*3*2*1. And 9! = 9*8*7*6*5*4*3*2*1. 16 | */ 17 | fun factorial(number: Int): Int { 18 | return when { 19 | (number < 0) -> 0 20 | (number <= 1) -> 1 21 | else -> { number * factorial(number.minus(1))} 22 | } 23 | } 24 | 25 | /** 26 | * O(2N) denotes an algorithm whose growth doubles with each addition to the input 27 | * data set. The growth curve of an O(2N) function is exponential - starting off 28 | * very shallow, then rising meteorically. 29 | * 30 | * @number: the nth number in the Fibonacci sequence. 31 | */ 32 | fun fibonacci(number: Int): Int { 33 | return when { 34 | (number <= 1) -> number 35 | else -> { fibonacci(number - 1) + fibonacci(number - 2) } 36 | } 37 | } 38 | } -------------------------------------------------------------------------------- /src/main/kotlin/com/fernandocejas/crackinginterview/string/StringProblems.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.string 2 | 3 | import kotlin.String 4 | 5 | /** 6 | * A good thing about the string is that if you know the array, you can solve string-based 7 | * questions easily because strings are nothing but a character array. 8 | */ 9 | class StringProblems { 10 | 11 | /** 12 | * PROBLEM: 13 | * How do you print duplicate characters from a string? 14 | * 15 | * SOLUTION: 16 | * Linear -> O(n) 17 | */ 18 | fun findDuplicates(string: String): String { 19 | var result = "" 20 | val charSet: MutableSet = hashSetOf() 21 | val stringWithoutSpaces = string.trim().replace(" ", "") 22 | 23 | stringWithoutSpaces.forEach { 24 | if (!charSet.add(it) && !result.contains(it)) { result += it } 25 | } 26 | 27 | return result 28 | } 29 | } -------------------------------------------------------------------------------- /src/main/kotlin/com/fernandocejas/crackinginterview/tree/Node.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.tree 2 | 3 | class Node(val data: T) { 4 | var left: Node? = null 5 | var right: Node? = null 6 | } 7 | 8 | -------------------------------------------------------------------------------- /src/main/kotlin/com/fernandocejas/crackinginterview/tree/Sample.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.tree 2 | 3 | class Sample { 4 | 5 | /** 6 | * Create the following tree structure: 7 | * 8 | * 3 9 | * / \ 10 | * 9 20 11 | * / \ 12 | * 15 7 13 | */ 14 | fun createBasicTree(): Node { 15 | 16 | val nineNode = Node(9) 17 | val fifteenNode = Node(15) 18 | val sevenNode = Node(7) 19 | 20 | val twentyNode = Node(20) 21 | twentyNode.left = fifteenNode 22 | twentyNode.right = sevenNode 23 | 24 | val rootNode = Node(3) 25 | rootNode.left = nineNode 26 | rootNode.right = twentyNode 27 | 28 | return rootNode 29 | } 30 | 31 | /** 32 | * Create the following BST structure: 33 | * 34 | * 2 35 | * / \ 36 | * 1 3 37 | */ 38 | fun createBasicBST(): Node { 39 | val rootNode = Node(2) 40 | rootNode.left = Node(1) 41 | rootNode.right = Node(3) 42 | 43 | return rootNode 44 | } 45 | 46 | /** 47 | * Create the following tree structure: 48 | * 49 | * 5 50 | * / \ 51 | * 1 4 52 | * / \ 53 | * 3 6 54 | */ 55 | fun createNoBST(): Node { 56 | 57 | val nineNode = Node(9) 58 | val fifteenNode = Node(15) 59 | val sevenNode = Node(7) 60 | 61 | val twentyNode = Node(20) 62 | twentyNode.left = fifteenNode 63 | twentyNode.right = sevenNode 64 | 65 | val rootNode = Node(3) 66 | rootNode.left = nineNode 67 | rootNode.right = twentyNode 68 | 69 | return rootNode 70 | } 71 | 72 | /** 73 | * Create the following tree structure: 74 | * 75 | * 3 76 | * / \ 77 | * 2 5 78 | * / \ 79 | * 1 4 80 | */ 81 | fun createTrickyNoBST(): Node { 82 | 83 | val oneNode = Node(1) 84 | val fourNode = Node(4) 85 | val fiveNode = Node(5) 86 | 87 | val twoNode = Node(2) 88 | twoNode.left = oneNode 89 | twoNode.right = fourNode 90 | 91 | val rootNode = Node(3) 92 | rootNode.left = twoNode 93 | rootNode.right = fiveNode 94 | 95 | return rootNode 96 | } 97 | } -------------------------------------------------------------------------------- /src/main/kotlin/com/fernandocejas/crackinginterview/tree/TreeProblems.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.tree 2 | 3 | class TreeProblems { 4 | 5 | /** 6 | * PROBLEM: 7 | * Given a binary tree, find its maximum depth. 8 | * 9 | * The maximum depth is the number of nodes along the longest path from the root node 10 | * down to the farthest leaf node. 11 | * Note: A leaf is a node with no children. 12 | * 13 | * SOLUTION: 14 | * Linear -> O(n) 15 | */ 16 | fun maxDepth(root: Node?): Int { 17 | return when (root == null) { 18 | true -> 0 19 | false -> { 20 | val leftDepth = maxDepth(root.left) 21 | val rightDepth = maxDepth(root.right) 22 | 23 | Math.max(leftDepth, rightDepth).plus(1) 24 | } 25 | } 26 | } 27 | 28 | fun isValidBST(root: Node?, min: Int = Int.MIN_VALUE, max: Int = Int.MAX_VALUE): Boolean { 29 | if (root == null) return true 30 | 31 | if (root.left != null && (root.left!!.data > root.data) || root.left!!.data < min) return false 32 | if (root.right != null && (root.right!!.data < root.data || root.right!!.data > max)) return false 33 | 34 | //TODO: Fix NPE left!!.data and right!!.data 35 | return (isValidBST(root.left, min, root.left!!.data) && isValidBST(root.right, max, root.right!!.data)) 36 | } 37 | } -------------------------------------------------------------------------------- /src/main/kotlin/com/fernandocejas/crackinginterview/util/Performance.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.util 2 | 3 | import kotlin.system.measureTimeMillis 4 | 5 | inline fun measureMillis(blockName: String = "Function", block: () -> Unit) { 6 | val timeMillis = measureTimeMillis { block() } 7 | println("Elapsed time for $blockName: $timeMillis millis.") 8 | } -------------------------------------------------------------------------------- /src/test/kotlin/com/fernandocejas/crackinginterview/array/ArrayProblemsTest.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.array 2 | 3 | import org.amshove.kluent.`should be equal to` 4 | import org.amshove.kluent.`should contain all` 5 | import org.amshove.kluent.`should equal` 6 | import org.junit.jupiter.api.Test 7 | 8 | 9 | 10 | internal class ArrayProblemsTest { 11 | 12 | private val array = ArrayProblems() 13 | 14 | @Test fun `find duplicate - brute force`() { 15 | array.findDuplicateBruteForce(arrayOf(3, 5, 8, 9, 11, 5, 4, 1, 6)) `should be equal to` 5 16 | array.findDuplicateBruteForce(arrayOf(3, 3)) `should be equal to` 3 17 | array.findDuplicateBruteForce(arrayOf(0, 4, 1, 1)) `should be equal to` 1 18 | } 19 | 20 | @Test fun `array with no duplicates should return -1 - brute force`() { 21 | array.findDuplicateBruteForce(arrayOf(0, 4, 1, 2)) `should be equal to` -1 22 | } 23 | 24 | @Test fun `find duplicate - better`() { 25 | array.findDuplicateBetter(arrayOf(3, 5, 8, 9, 11, 5, 4, 1, 6)) `should be equal to` 5 26 | array.findDuplicateBetter(arrayOf(3, 3)) `should be equal to` 3 27 | array.findDuplicateBetter(arrayOf(0, 4, 1, 1)) `should be equal to` 1 28 | } 29 | 30 | @Test fun `array with no duplicates should return -1 - better`() { 31 | array.findDuplicateBetter(arrayOf(0, 4, 1, 2)) `should be equal to` -1 32 | } 33 | 34 | @Test fun `should remove duplicates - using Set`() { 35 | array.removeDuplicatesUsingSet(arrayOf(0, 0, 0, 1)) `should contain all` arrayOf(0, 1) 36 | array.removeDuplicatesUsingSet(arrayOf(1, 2, 3)) `should contain all` arrayOf(1, 2, 3) 37 | array.removeDuplicatesUsingSet(arrayOf(2, 2, 4, 4, 4, 5, 5)) `should contain all` arrayOf(2, 4, 5) 38 | } 39 | 40 | @Test fun `should remove duplicates`() { 41 | array.removeDuplicates(arrayOf(0, 0, 0, 1)) `should contain all` arrayOf(0, 1) 42 | array.removeDuplicates(arrayOf(1, 2, 3)) `should contain all` arrayOf(1, 2, 3) 43 | array.removeDuplicates(arrayOf(2, 2, 4, 4, 4, 5, 5)) `should contain all` arrayOf(2, 4, 5) 44 | } 45 | 46 | @Test fun `should reverse array using language built in functionality`() { 47 | array.reverseKotlin(arrayOf(2, 9, 0, 4, 2, 8, 1)) `should equal` arrayOf(1, 8, 2, 4, 0, 9, 2) 48 | array.reverseKotlin(arrayOf(1, 2, 3)) `should equal` arrayOf(3, 2, 1) 49 | array.reverseKotlin(arrayOf(0, 0, 1, 1)) `should equal` arrayOf(1, 1, 0, 0) 50 | array.reverseKotlin(arrayOf(10, 11)) `should equal` arrayOf(11, 10) 51 | } 52 | 53 | @Test fun `should reverse array`() { 54 | array.reverse(arrayOf(2, 9, 0, 4, 2, 8, 1)) `should equal` arrayOf(1, 8, 2, 4, 0, 9, 2) 55 | array.reverse(arrayOf(1, 2, 3)) `should equal` arrayOf(3, 2, 1) 56 | array.reverse(arrayOf(0, 0, 1, 1)) `should equal` arrayOf(1, 1, 0, 0) 57 | array.reverse(arrayOf(10, 11)) `should equal` arrayOf(11, 10) 58 | array.reverse(arrayOf("One", "Two", "Three")) `should equal` arrayOf("Three", "Two", "One") 59 | } 60 | } -------------------------------------------------------------------------------- /src/test/kotlin/com/fernandocejas/crackinginterview/list/LinkedListProblemsTest.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.list 2 | 3 | import org.amshove.kluent.`should be equal to` 4 | import org.junit.jupiter.api.Test 5 | 6 | internal class LinkedListProblemsTest { 7 | 8 | private val linkedList = LinkedListProblems() 9 | 10 | @Test fun `find middle element happy cases`() { 11 | val myLinkedListOne = java.util.LinkedList() 12 | myLinkedListOne.add("One") 13 | myLinkedListOne.add("Two") 14 | myLinkedListOne.add("Three") 15 | linkedList.findMiddleElement(myLinkedListOne) `should be equal to` "Three" 16 | 17 | val myLinkedListTwo = java.util.LinkedList() 18 | myLinkedListTwo.add(1) 19 | myLinkedListTwo.add(2) 20 | myLinkedListTwo.add(3) 21 | myLinkedListTwo.add(4) 22 | linkedList.findMiddleElement(myLinkedListTwo) `should be equal to` 3 23 | } 24 | } -------------------------------------------------------------------------------- /src/test/kotlin/com/fernandocejas/crackinginterview/list/MyLinkedListProblemsTest.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.list 2 | 3 | import org.amshove.kluent.`should be equal to` 4 | import org.junit.jupiter.api.Test 5 | 6 | internal class MyLinkedListProblemsTest { 7 | 8 | @Test fun `should be empty when creating a new linked list`() { 9 | val myLinkedList = LinkedList() 10 | 11 | myLinkedList.isEmpty() `should be equal to` true 12 | myLinkedList.size() `should be equal to` 0 13 | } 14 | } -------------------------------------------------------------------------------- /src/test/kotlin/com/fernandocejas/crackinginterview/recursion/RecursionProblemsTest.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.recursion 2 | 3 | import org.amshove.kluent.`should equal` 4 | import org.junit.jupiter.api.Test 5 | 6 | internal class RecursionProblemsTest { 7 | 8 | private val recursionProblems = RecursionProblems() 9 | 10 | @Test fun `factorial happy case`() { 11 | recursionProblems.factorial(5) `should equal` 120 12 | } 13 | 14 | @Test fun `factorial of negative number should be zero`() { 15 | recursionProblems.factorial(-1) `should equal` 0 16 | } 17 | 18 | @Test fun `factorial of zero should one`() { 19 | recursionProblems.factorial(0) `should equal` 1 20 | } 21 | 22 | @Test fun `fibonacci happy case`() { 23 | recursionProblems.fibonacci(7) `should equal` 13 24 | } 25 | } -------------------------------------------------------------------------------- /src/test/kotlin/com/fernandocejas/crackinginterview/string/StringProblemsTest.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.string 2 | 3 | import org.amshove.kluent.`should be equal to` 4 | import org.junit.jupiter.api.Test 5 | 6 | internal class StringProblemsTest { 7 | 8 | private val stringProblems = StringProblems() 9 | 10 | @Test fun `should find duplicate characters`() { 11 | stringProblems.findDuplicates("holaah") `should be equal to` "ah" 12 | stringProblems.findDuplicates("asdfg") `should be equal to` "" 13 | stringProblems.findDuplicates("This is another sentence") `should be equal to` "ishent" 14 | } 15 | } -------------------------------------------------------------------------------- /src/test/kotlin/com/fernandocejas/crackinginterview/tree/TreeProblemsTest.kt: -------------------------------------------------------------------------------- 1 | package com.fernandocejas.crackinginterview.tree 2 | 3 | import org.amshove.kluent.`should be` 4 | import org.amshove.kluent.`should equal` 5 | import org.junit.jupiter.api.Test 6 | 7 | internal class TreeProblemsTest { 8 | private val treeProblems = TreeProblems() 9 | private val treeSamples = Sample() 10 | 11 | @Test fun `should return max depth`() { 12 | treeProblems.maxDepth(treeSamples.createBasicBST()) `should equal` 2 13 | treeProblems.maxDepth(treeSamples.createBasicTree()) `should equal` 3 14 | } 15 | 16 | @Test fun `should validate a BST`() { 17 | treeProblems.isValidBST(treeSamples.createBasicBST()) `should be` true 18 | treeProblems.isValidBST(treeSamples.createNoBST()) `should be` false 19 | treeProblems.isValidBST(treeSamples.createTrickyNoBST()) `should be` false 20 | } 21 | } --------------------------------------------------------------------------------