├── .gitignore ├── .travis.yml ├── LICENSE ├── README.md ├── build.gradle ├── gradle └── wrapper │ ├── gradle-wrapper.jar │ └── gradle-wrapper.properties ├── gradlew ├── gradlew.bat ├── settings.gradle └── src ├── main └── java │ └── com │ └── fisher │ └── coder │ ├── chapter1 │ ├── ReverseString.java │ ├── _1_1.java │ ├── _1_2.java │ ├── _1_3.java │ ├── _1_5.java │ └── _1_6.java │ ├── chapter2 │ └── _2_1.java │ ├── chapter4 │ └── _4_4.java │ ├── chapter8 │ └── _8_1.java │ └── common │ └── classes │ ├── ListNode.java │ └── TreeNode.java └── test └── java └── com └── fisher └── coder ├── chapter1 ├── ReverseStringTest.java ├── _1_1_test.java ├── _1_2_test.java ├── _1_3_test.java ├── _1_5_test.java └── _1_6_test.java ├── chapter2 └── _2_1_test.java ├── chapter4 └── _4_1_test.java └── chapter8 └── _8_1_test.java /.gitignore: -------------------------------------------------------------------------------- 1 | .idea 2 | .gradle 3 | 4 | -------------------------------------------------------------------------------- /.travis.yml: -------------------------------------------------------------------------------- 1 | language: java 2 | 3 | jdk: 4 | - oraclejdk8 5 | 6 | script: gradle check clean build 7 | 8 | notifications: 9 | email: 10 | recipients: 11 | - fishercoder@gmail.com 12 | on_failure: always 13 | 14 | -------------------------------------------------------------------------------- /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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do 14 | ls=`ls -ld "$PRG"` 15 | link=`expr "$ls" : '.*-> \(.*\)$'` 16 | if expr "$link" : '/.*' > /dev/null; then 17 | PRG="$link" 18 | else 19 | PRG=`dirname "$PRG"`"/$link" 20 | fi 21 | done 22 | SAVED="`pwd`" 23 | cd "`dirname \"$PRG\"`/" >/dev/null 24 | APP_HOME="`pwd -P`" 25 | cd "$SAVED" >/dev/null 26 | 27 | APP_NAME="Gradle" 28 | APP_BASE_NAME=`basename "$0"` 29 | 30 | # Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script. 31 | DEFAULT_JVM_OPTS="" 32 | 33 | # Use the maximum available, or set MAX_FD != -1 to use that value. 34 | MAX_FD="maximum" 35 | 36 | warn ( ) { 37 | echo "$*" 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 | # Split up the JVM_OPTS And GRADLE_OPTS values into an array, following the shell quoting and substitution rules 158 | function splitJvmOpts() { 159 | JVM_OPTS=("$@") 160 | } 161 | eval splitJvmOpts $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS 162 | JVM_OPTS[${#JVM_OPTS[*]}]="-Dorg.gradle.appname=$APP_BASE_NAME" 163 | 164 | # by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong 165 | if [[ "$(uname)" == "Darwin" ]] && [[ "$HOME" == "$PWD" ]]; then 166 | cd "$(dirname "$0")" 167 | fi 168 | 169 | exec "$JAVACMD" "${JVM_OPTS[@]}" -classpath "$CLASSPATH" org.gradle.wrapper.GradleWrapperMain "$@" 170 | -------------------------------------------------------------------------------- /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 | -------------------------------------------------------------------------------- /settings.gradle: -------------------------------------------------------------------------------- 1 | rootProject.name = 'ctci' 2 | 3 | -------------------------------------------------------------------------------- /src/main/java/com/fisher/coder/chapter1/ReverseString.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter1; 2 | 3 | /** 4 | * Created by stevesun on 4/16/17. 5 | */ 6 | public class ReverseString { 7 | /**Implement a function void reverse(char* str) in C or C++ which reverses a null-terminated string.*/ 8 | 9 | //For consistency, I'm implementing it in Java. Principles apply in C or C++. 10 | public static String reverse(String str) { 11 | int left = 0; 12 | int right = str.length()-1; 13 | char[] chars = str.toCharArray(); 14 | while (left < right) { 15 | char temp = chars[left]; 16 | chars[left] = chars[right]; 17 | chars[right] = temp; 18 | left++; 19 | right--; 20 | } 21 | return new String(chars); 22 | } 23 | } 24 | -------------------------------------------------------------------------------- /src/main/java/com/fisher/coder/chapter1/_1_1.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter1; 2 | 3 | import java.util.HashSet; 4 | import java.util.Set; 5 | 6 | /** 7 | * Created by stevesun on 4/15/17. 8 | */ 9 | public class _1_1 { 10 | 11 | /**Implement an algorithm to determine if a string has all unique charaters. 12 | * What if you cannot use additional data structures?*/ 13 | 14 | 15 | /**First, ask your interviewer if this string is an ASCII string or a Unicode string, this shows your deep 16 | * understanding of CS.*/ 17 | 18 | /**Solution 1: use Set 19 | * Time: O(n) 20 | * Space: O(n) 21 | * */ 22 | public static boolean hasAllUniqueChars_use_set(String str) { 23 | Set set = new HashSet<>(); 24 | for (char c : str.toCharArray()) { 25 | if (!set.add(c)) return false; 26 | } 27 | return true; 28 | } 29 | 30 | /**Solution 2: use a boolean array to represent every char, only an array of 256 size is needed. 31 | * Time: O(n) 32 | * Space: O(1) 33 | * */ 34 | public static boolean hasAllUniqueChars_use_boolean_array(String str) { 35 | if (str.length() > 256) return false; 36 | boolean[] chars = new boolean[256]; 37 | for (char c : str.toCharArray()) { 38 | if (!chars[c - 'a']) chars[c - 'a'] = true; 39 | else if (chars[c - 'a']) return false; 40 | } 41 | return true; 42 | } 43 | 44 | /**Solution 3: use bit (assuming this string only uses lowercase letters a through z), 45 | * so we could use only one int to represent this string*/ 46 | public static boolean hasAllUniqueChars_use_bit(String str) { 47 | int checker = 0; 48 | for (int i = 0; i < str.length(); i++) { 49 | int val = str.charAt(i) - 'a'; 50 | if ((checker & (1 << val)) > 0) return false;//this is to check if (1 << val) already existed in checker, if so, that means this char has already showed up in previous substrings 51 | checker |= (1 << val);//if not, we store (1 << val) in checker: exclusive or '|' does this perfectly! 52 | } 53 | return true; 54 | } 55 | } 56 | -------------------------------------------------------------------------------- /src/main/java/com/fisher/coder/chapter1/_1_2.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter1; 2 | 3 | /** 4 | * Created by stevesun on 4/16/17. 5 | */ 6 | public class _1_2 { 7 | /**Given two strings, write a method to decide if one is a permuation of the other.*/ 8 | 9 | public static boolean isPermutation(String a, String b) { 10 | if (a.length() != b.length()) return false; 11 | //ask your interviewer if the two strings are ASCII first before you use 256 as the array length 12 | int[] count = new int[256]; 13 | for (char c : a.toCharArray()) { 14 | count[c - 'a']++; 15 | } 16 | for (char c : b.toCharArray()) { 17 | count[c - 'a']--; 18 | } 19 | for (int i : count) { 20 | if (i != 0) return false; 21 | } 22 | return true; 23 | } 24 | } 25 | -------------------------------------------------------------------------------- /src/main/java/com/fisher/coder/chapter1/_1_3.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter1; 2 | 3 | /** 4 | * Created by stevesun on 4/16/17. 5 | */ 6 | public class _1_3 { 7 | /**Write a method to replace all spaces in a string with '20%'. You may assume that the string has sufficient space at the end 8 | * of the string to hold the additional characters, and that you are given the "true" length of the string. 9 | * (Note: if implementing in Java, please use a character array so that you can perform this operation in place.) 10 | * 11 | * Example: 12 | * Input: "Mr John Smith " 13 | * Output: "Mr%20John%20Smith"*/ 14 | 15 | public static String replaceWhitespace_use_javaUtil(String original) { 16 | return original.replace(" ", "%20"); 17 | } 18 | 19 | public static String replaceWhitespace_use_plain_java(String original) { 20 | StringBuilder stringBuilder = new StringBuilder(); 21 | for (char c : original.toCharArray()) { 22 | if (c == ' ') { 23 | stringBuilder.append("%20"); 24 | } else { 25 | stringBuilder.append(c); 26 | } 27 | } 28 | return stringBuilder.toString(); 29 | } 30 | } 31 | -------------------------------------------------------------------------------- /src/main/java/com/fisher/coder/chapter1/_1_5.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter1; 2 | 3 | /** 4 | * Created by stevesun on 4/21/17. 5 | */ 6 | public class _1_5 { 7 | 8 | /**One away: 9 | * There are three types of edits that can be performed on strings: 10 | * insert a character, remove a character or replace a character. 11 | * Given two strings, write a function to check if they are one edit (or zero) edits away. 12 | * 13 | * Example: 14 | * pale, ple -> true 15 | * pales, pale -> true 16 | * pale, bale -> true 17 | * pale, bake -> false*/ 18 | 19 | public static boolean oneAway(String a, String b) { 20 | 21 | //credit: https://discuss.leetcode.com/topic/18392/accepted-clean-java-solution-with-explanation-two-pointers 22 | if (a == null || a.isEmpty()) return b == null || b.length() == 1; 23 | if (b == null || b.isEmpty()) return a == null || a.length() == 1; 24 | 25 | if (a.length() > b.length()) return oneAway(b, a);//make sure a is always shorter than b 26 | 27 | int i = 0; 28 | int j = 0; 29 | while (i < a.length() && j < b.length()) { 30 | if (a.charAt(i) != b.charAt(j)) { 31 | /**a is the shorter one, when we found there's a char that is different between a and b, 32 | the only two possibilities that these two strings are one edit away is these two cases: 33 | 1. a.substring(i+1).equals(b.substring(j+1)) 34 | 2. a.substring(i).equals(b.substring(j+1)) 35 | */ 36 | return a.substring(i+1).equals(b.substring(j+1)) || a.substring(i).equals(b.substring(j+1)); 37 | } 38 | i++; 39 | j++; 40 | } 41 | /**When jump out of the for loop, there should be only one char left in the longer string b, otherwise return false.*/ 42 | return b.length() - j == 1; 43 | 44 | } 45 | } 46 | -------------------------------------------------------------------------------- /src/main/java/com/fisher/coder/chapter1/_1_6.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter1; 2 | 3 | /** 4 | * Created by stevesun on 4/16/17. 5 | */ 6 | public class _1_6 { 7 | /**Implement a method to perform basic string compression using the counts of repeated characters. 8 | * For example, the string aabcccccaaa would become a2b1c5a3. 9 | * If the "compressed" string would not become smaller than the original string, your method should return the original string.*/ 10 | 11 | public static String stringCompression(String original) { 12 | StringBuilder stringBuilder = new StringBuilder(); 13 | char last = original.charAt(0); 14 | int count = 1; 15 | for (int i = 1; i < original.length(); i++) { 16 | if (last == original.charAt(i)) { 17 | count++; 18 | } else { 19 | stringBuilder.append(last); 20 | stringBuilder.append(count); 21 | last = original.charAt(i); 22 | count = 1; 23 | } 24 | } 25 | stringBuilder.append(last); 26 | stringBuilder.append(count); 27 | if (stringBuilder.toString().length() >= original.length()) return original; 28 | return stringBuilder.toString(); 29 | } 30 | } 31 | -------------------------------------------------------------------------------- /src/main/java/com/fisher/coder/chapter2/_2_1.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter2; 2 | 3 | import com.fisher.coder.common.classes.ListNode; 4 | 5 | import java.util.HashSet; 6 | import java.util.Set; 7 | 8 | /** 9 | * Created by stevesun on 4/18/17. 10 | */ 11 | public class _2_1 { 12 | /**Remove Dups: 13 | * Write code to remove duplicates from an unsorted linked list. 14 | * 15 | * Follow up: 16 | * How would you solve this problem if a temporary buffer is not allowed.*/ 17 | 18 | public static ListNode removeDups_use_additional_buffer(ListNode head) { 19 | Set set = new HashSet<>(); 20 | ListNode tmp = new ListNode(-1); 21 | tmp.next = head; 22 | ListNode prev = null; 23 | while (head != null) { 24 | if (set.contains(head.val)) { 25 | prev.next = head.next; 26 | } else { 27 | set.add(head.val); 28 | prev = head; 29 | } 30 | head = head.next; 31 | } 32 | return tmp.next; 33 | } 34 | 35 | /**I think below method is superior than the method listed in CtCI 6th edition, since it traverses the list only once.*/ 36 | public static ListNode removeDups_no_additional_buffer(ListNode head) { 37 | ListNode tmp = new ListNode(-1); 38 | tmp.next = head; 39 | while (head != null) { 40 | while (head.next != null && head.val == head.next.val) { 41 | head.next = head.next.next; 42 | } 43 | head = head.next; 44 | } 45 | return tmp.next; 46 | } 47 | } 48 | -------------------------------------------------------------------------------- /src/main/java/com/fisher/coder/chapter4/_4_4.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter4; 2 | 3 | import com.fisher.coder.common.classes.TreeNode; 4 | 5 | /** 6 | * Created by stevesun on 4/15/17. 7 | */ 8 | public class _4_4 { 9 | /** 10 | * Question: 11 | * 12 | * Implement a function to check if a binary tree is balanced. 13 | * For the purposes of this question, a balanced tree is defined to be a tree such that 14 | * the heights of the two subtrees of any node never differ by more than one.*/ 15 | 16 | //The most naive way: calculate the heights of each node and check if it meets the requirement 17 | //But this is O(n^2) 18 | public static boolean isBalanced(TreeNode root) { 19 | if (root == null) return true; 20 | if (Math.abs(getH(root.left) - getH(root.right)) > 1) return false; 21 | else return isBalanced(root.left) && isBalanced(root.right); 22 | } 23 | 24 | private static int getH(TreeNode root) { 25 | if (root == null) return 0; 26 | int leftH = getH(root.left); 27 | int rightH = getH(root.right); 28 | return Math.max(leftH, rightH)+1; 29 | } 30 | 31 | 32 | static class ImprovedSolution { 33 | /**We could improve the above solution by saving some calls to getH() method: 34 | * while traversing the subtrees, as soon as we find any subtrees that don't meet the requirement, we could just exit.*/ 35 | public static boolean isBalanced(TreeNode root) { 36 | return getH(root) != -1; 37 | } 38 | 39 | public static int getH(TreeNode root) { 40 | if (root == null) return 0; 41 | int leftH = 0; 42 | if (root.left != null) leftH = getH(root.left); 43 | if (leftH == -1) return -1; 44 | int rightH = 0; 45 | if (root.right != null) rightH = getH(root.right); 46 | if (rightH == -1) return -1; 47 | if (Math.abs(leftH - rightH) > 1) return -1; 48 | return Math.max(leftH, rightH) + 1; 49 | } 50 | } 51 | 52 | } 53 | -------------------------------------------------------------------------------- /src/main/java/com/fisher/coder/chapter8/_8_1.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter8; 2 | 3 | /** 4 | * Created by stevesun on 4/16/17. 5 | */ 6 | public class _8_1 { 7 | /**A child is running up a staircase with n steps, and can hop either 1 step, 2 steps, or 3 steps at a time. 8 | * Implement a method to count how many possible ways the child can run up the stairs.*/ 9 | 10 | public static int ways(int n) { 11 | if (n < 3) return n; 12 | int[] dp = new int[n]; 13 | dp[0] = 1; 14 | dp[1] = 2; 15 | dp[2] = 3; 16 | for (int i = 3; i < n; i++) { 17 | dp[i] = dp[i-1] + dp[i-2] + dp[i-3]; 18 | } 19 | return dp[n-1]; 20 | } 21 | } 22 | -------------------------------------------------------------------------------- /src/main/java/com/fisher/coder/common/classes/ListNode.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.common.classes; 2 | 3 | import java.util.List; 4 | 5 | /** 6 | * Normally, both val and next should be private attributes and generate getter and setter for them, 7 | * but for the convenience of leetcode solutions, I set them as public. 8 | */ 9 | public class ListNode { 10 | public int val; 11 | public ListNode next; 12 | 13 | public ListNode(int i) { 14 | this.val = i; 15 | } 16 | 17 | public int val() { 18 | return val; 19 | } 20 | 21 | public static ListNode createSinglyLinkedList() { 22 | ListNode head = new ListNode(1); 23 | 24 | ListNode node1 = new ListNode(2); 25 | head.next = node1; 26 | 27 | ListNode node2 = new ListNode(3); 28 | node1.next = node2; 29 | 30 | ListNode node3 = new ListNode(4); 31 | node2.next = node3; 32 | 33 | ListNode node4 = new ListNode(5); 34 | node3.next = node4; 35 | 36 | ListNode node5 = new ListNode(6); 37 | node4.next = node5; 38 | 39 | ListNode node6 = new ListNode(7); 40 | node5.next = node6; 41 | 42 | ListNode node7 = new ListNode(8); 43 | node6.next = node7; 44 | 45 | ListNode node8 = new ListNode(9); 46 | node7.next = node8; 47 | 48 | ListNode node9 = new ListNode(10); 49 | node8.next = node9; 50 | return head; 51 | } 52 | 53 | /**TODO: this function is NOT working as supposed to, I need to fix it! Commit from my Windows machine!*/ 54 | public static ListNode createSinglyLinkedList(List listValues) { 55 | if (listValues == null || listValues.size() == 0) 56 | throw new IllegalArgumentException( 57 | "Please pass in a valid listValues to create a singly linked list."); 58 | ListNode head = new ListNode(listValues.get(0)); 59 | for(int i : listValues){ 60 | appendNode(head, i); 61 | } 62 | printList(head); 63 | return head; 64 | } 65 | 66 | @Override 67 | public boolean equals(Object o) { 68 | if (this == o) return true; 69 | if (!(o instanceof ListNode)) return false; 70 | 71 | ListNode listNode = (ListNode) o; 72 | 73 | if (val != listNode.val) return false; 74 | return next != null ? next.equals(listNode.next) : listNode.next == null; 75 | } 76 | 77 | @Override 78 | public int hashCode() { 79 | int result = val; 80 | result = 31 * result + (next != null ? next.hashCode() : 0); 81 | return result; 82 | } 83 | 84 | @Override 85 | public String toString() { 86 | 87 | return "ListNode{" + 88 | "val=" + val + 89 | ", next=" + next + 90 | '}'; 91 | } 92 | 93 | private static void appendNode(ListNode head, int i) { 94 | ListNode node = new ListNode(i); 95 | head.next = node; 96 | // head = head.next; 97 | } 98 | 99 | public static void printList(ListNode head) { 100 | ListNode temp = head; 101 | System.out.println(); 102 | while (temp != null) { 103 | System.out.print(temp.val() + "\t"); 104 | temp = temp.next; 105 | } 106 | } 107 | } 108 | -------------------------------------------------------------------------------- /src/main/java/com/fisher/coder/common/classes/TreeNode.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.common.classes; 2 | 3 | public class TreeNode { 4 | public int val; 5 | public TreeNode left; 6 | public TreeNode right; 7 | 8 | @Override 9 | public String toString() { 10 | return "TreeNode{" + 11 | "val=" + val + 12 | ", left=" + left + 13 | ", right=" + right + 14 | '}'; 15 | } 16 | 17 | public TreeNode(int x){this.val = x;} 18 | 19 | public TreeNode(){} 20 | 21 | public TreeNode(TreeNode left, int val, TreeNode right) { 22 | this.left = left; 23 | this.val = val; 24 | this.right = right; 25 | } 26 | } 27 | -------------------------------------------------------------------------------- /src/test/java/com/fisher/coder/chapter1/ReverseStringTest.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter1; 2 | 3 | import org.junit.Assert; 4 | import org.junit.Test; 5 | 6 | /** 7 | * Created by stevesun on 4/15/17. 8 | */ 9 | public class ReverseStringTest { 10 | 11 | @Test 12 | public void test1() { 13 | String str = "abcda"; 14 | String reverseStr = new StringBuilder(str).reverse().toString(); 15 | Assert.assertEquals(ReverseString.reverse(str), reverseStr); 16 | } 17 | } 18 | -------------------------------------------------------------------------------- /src/test/java/com/fisher/coder/chapter1/_1_1_test.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter1; 2 | 3 | import org.junit.Assert; 4 | import org.junit.Test; 5 | 6 | /** 7 | * Created by stevesun on 4/15/17. 8 | */ 9 | public class _1_1_test { 10 | 11 | @Test 12 | public void test1() { 13 | Assert.assertEquals(_1_1.hasAllUniqueChars_use_set("abcda"), false); 14 | Assert.assertEquals(_1_1.hasAllUniqueChars_use_boolean_array("abcda"), false); 15 | Assert.assertEquals(_1_1.hasAllUniqueChars_use_bit("abcda"), false); 16 | } 17 | } 18 | -------------------------------------------------------------------------------- /src/test/java/com/fisher/coder/chapter1/_1_2_test.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter1; 2 | 3 | import org.junit.Assert; 4 | import org.junit.Test; 5 | 6 | /** 7 | * Created by stevesun on 4/15/17. 8 | */ 9 | public class _1_2_test { 10 | 11 | @Test 12 | public void test1() { 13 | String a = "abcda"; 14 | String b = "caadb"; 15 | Assert.assertEquals(_1_2.isPermutation(a, b), true); 16 | } 17 | 18 | @Test 19 | public void test2() { 20 | String a = "abcdaaa"; 21 | String b = "caadb"; 22 | Assert.assertEquals(_1_2.isPermutation(a, b), false); 23 | } 24 | } 25 | -------------------------------------------------------------------------------- /src/test/java/com/fisher/coder/chapter1/_1_3_test.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter1; 2 | 3 | import org.junit.Assert; 4 | import org.junit.Test; 5 | 6 | /** 7 | * Created by stevesun on 4/15/17. 8 | */ 9 | public class _1_3_test { 10 | 11 | @Test 12 | public void test1() { 13 | String str = "Mr John Smith"; 14 | String replacedStr = "Mr%20John%20Smith"; 15 | Assert.assertEquals(_1_3.replaceWhitespace_use_javaUtil(str), replacedStr); 16 | Assert.assertEquals(_1_3.replaceWhitespace_use_plain_java(str), replacedStr); 17 | } 18 | } 19 | -------------------------------------------------------------------------------- /src/test/java/com/fisher/coder/chapter1/_1_5_test.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter1; 2 | 3 | import org.junit.Assert; 4 | import org.junit.Test; 5 | 6 | public class _1_5_test { 7 | 8 | @Test 9 | public void test1() { 10 | Assert.assertEquals(true, _1_5.oneAway("a", "")); 11 | } 12 | 13 | @Test 14 | public void test2() { 15 | Assert.assertEquals(true, _1_5.oneAway("a", "ac")); 16 | } 17 | } 18 | -------------------------------------------------------------------------------- /src/test/java/com/fisher/coder/chapter1/_1_6_test.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter1; 2 | 3 | import org.junit.Assert; 4 | import org.junit.Test; 5 | 6 | /** 7 | * Created by stevesun on 4/15/17. 8 | */ 9 | public class _1_6_test { 10 | 11 | @Test 12 | public void test1() { 13 | String str = "aabcccccaaa"; 14 | String expectedCompressedStr = "a2b1c5a3"; 15 | Assert.assertEquals(expectedCompressedStr, _1_6.stringCompression(str)); 16 | } 17 | 18 | @Test 19 | public void test2() { 20 | String str = "aa"; 21 | String expectedCompressedStr = "aa"; 22 | Assert.assertEquals(expectedCompressedStr, _1_6.stringCompression(str)); 23 | } 24 | 25 | @Test 26 | public void test3() { 27 | String str = "aab"; 28 | String expectedCompressedStr = "aab"; 29 | Assert.assertEquals(expectedCompressedStr, _1_6.stringCompression(str)); 30 | } 31 | } 32 | -------------------------------------------------------------------------------- /src/test/java/com/fisher/coder/chapter2/_2_1_test.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter2; 2 | 3 | import com.fisher.coder.common.classes.ListNode; 4 | import org.junit.Assert; 5 | import org.junit.Test; 6 | 7 | /** 8 | * Created by stevesun on 4/18/17. 9 | */ 10 | public class _2_1_test { 11 | 12 | @Test 13 | public void test1() { 14 | ListNode node = new ListNode(1); 15 | node.next = new ListNode(2); 16 | node.next.next = new ListNode(2); 17 | 18 | ListNode expected = new ListNode(1); 19 | expected.next = new ListNode(2); 20 | 21 | Assert.assertEquals(expected, _2_1.removeDups_use_additional_buffer(node)); 22 | Assert.assertEquals(expected, _2_1.removeDups_no_additional_buffer(node)); 23 | } 24 | } 25 | -------------------------------------------------------------------------------- /src/test/java/com/fisher/coder/chapter4/_4_1_test.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter4; 2 | 3 | import com.fisher.coder.common.classes.TreeNode; 4 | import org.junit.Assert; 5 | import org.junit.Test; 6 | 7 | public class _4_1_test { 8 | 9 | @Test 10 | public void test1() { 11 | TreeNode root = new TreeNode(); 12 | Assert.assertEquals(true, _4_4.isBalanced(root)); 13 | Assert.assertEquals(true, _4_4.ImprovedSolution.isBalanced(root)); 14 | } 15 | 16 | @Test 17 | public void test2() { 18 | TreeNode root = new TreeNode(1); 19 | root.left = new TreeNode(2); 20 | root.left.left = new TreeNode(3); 21 | root.left.left.left = new TreeNode(4); 22 | root.right = new TreeNode(2); 23 | root.right.right = new TreeNode(3); 24 | root.right.right.right = new TreeNode(4); 25 | // Assert.assertEquals(false, _4_4.isBalanced(root));//might occasionally get StackOverflow error, so comment out 26 | Assert.assertEquals(false, _4_4.ImprovedSolution.isBalanced(root)); 27 | } 28 | } 29 | -------------------------------------------------------------------------------- /src/test/java/com/fisher/coder/chapter8/_8_1_test.java: -------------------------------------------------------------------------------- 1 | package com.fisher.coder.chapter8; 2 | 3 | import org.junit.Assert; 4 | import org.junit.Test; 5 | 6 | /** 7 | * Created by stevesun on 4/15/17. 8 | */ 9 | public class _8_1_test { 10 | 11 | @Test 12 | public void test1() { 13 | int n = 1; 14 | int expectedWays = 1; 15 | Assert.assertEquals(expectedWays, _8_1.ways(n)); 16 | } 17 | } 18 | --------------------------------------------------------------------------------