├── LICENSE ├── README.md └── top-interview-questions-easy ├── array ├── buyandsell.ts ├── containsduplicate.ts ├── duplicates.ts ├── intersectiontwoarrays.ts ├── movezeroes.ts ├── plusone.ts ├── rotatearray.ts ├── rotateimage.ts ├── singlenumber.ts ├── twosum.ts └── validsudoku.ts ├── design ├── minstack.ts └── shuffleanarray.ts ├── dynamic-programming ├── besttimetobuyandsell.ts ├── climbingstairs.ts ├── houserobber.ts └── maximumsubarray.ts ├── linkedlist ├── deletenodeinlinkedlist.ts ├── linkedlistcycle.ts ├── mergetwosortedlists.ts ├── palindromelinkedlist.ts ├── removenthnode.ts └── reverselinkedlist.ts ├── math ├── countprimes.ts ├── fizzbuzz.ts ├── powerofthree.ts └── romantointeger.ts ├── others ├── hammingdistance.ts ├── missingnumber.ts ├── numberof1bits.ts ├── pascaltriangle.ts ├── reversebits.ts └── validparenthesis.ts ├── sorted-and-searching ├── firstbadversion.ts └── mergesortedarray.ts ├── strings ├── atoi.ts ├── countandsay.ts ├── firstuniquechar.ts ├── longestcommonprefix.ts ├── reverseinteger.ts ├── reversestring.ts ├── strStr.ts ├── validanagram.ts └── validpalindrome.ts └── trees ├── binarytreelevelordertraversal.ts ├── convertsortedarraytotree.ts ├── maxdepthofbinarytree.ts ├── ordertraversal.ts ├── symmetrictree.ts └── validatebinarysearchtree.ts /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 2, June 1991 3 | 4 | Copyright (C) 1989, 1991 Free Software Foundation, Inc., 5 | 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 6 | Everyone is permitted to copy and distribute verbatim copies 7 | of this license document, but changing it is not allowed. 8 | 9 | Preamble 10 | 11 | The licenses for most software are designed to take away your 12 | freedom to share and change it. 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If this is what you want to do, use the GNU Lesser General 339 | Public License instead of this License. 340 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # leetcode 2 | 3 | Leetcode solutions in Typescript 4 | 5 | ## Collections 6 | 7 | [Top Interview Questions (Easy)](/top-interview-questions-easy) 8 | -------------------------------------------------------------------------------- /top-interview-questions-easy/array/buyandsell.ts: -------------------------------------------------------------------------------- 1 | // Best Time to Buy and Sell II 2 | function maxProfit(prices: number[]): number { 3 | let maxprofit: number = 0; 4 | for (let i: number = 1; i < prices.length; i++) { 5 | if (prices[i] > prices[i - 1]) 6 | maxprofit += prices[i] - prices[i - 1]; 7 | } 8 | return maxprofit; 9 | } -------------------------------------------------------------------------------- /top-interview-questions-easy/array/containsduplicate.ts: -------------------------------------------------------------------------------- 1 | // Contains Duplicate O(n^2) 2 | function containsDuplicate(nums: number[]): boolean { 3 | for (let i: number = 0; i < nums.length; ++i) { 4 | for (let j: number = 0; j < i; ++j) { 5 | if (nums[j] == nums[i]) return true; 6 | } 7 | } 8 | return false; 9 | } 10 | 11 | // Attempt at O(n log n) sorting; doesn't work 12 | // function containsDuplicate(nums: number[]): boolean { 13 | // let sortedArray: number[] = nums.sort((n1, n2) => n1 - 1); 14 | // for (let i: number = 0; i < sortedArray.length - 1; ++i) 15 | // if (sortedArray[i] == sortedArray[i + 1]) return true; 16 | // return false; 17 | // } 18 | 19 | // Attempt at O(n) with object/hashtable; couldn't get it to work hopefully will revisit soon 20 | // function containsDuplicate(nums: number[]): boolean { 21 | // const map: object = {} 22 | // for (let x of nums) { 23 | // if (x in map) return true; 24 | // map[x] = x; 25 | // } 26 | // return false; 27 | // }; -------------------------------------------------------------------------------- /top-interview-questions-easy/array/duplicates.ts: -------------------------------------------------------------------------------- 1 | // Remove Duplicates from Sorted Array 2 | function removeDuplicates(nums: number[]): number { 3 | if (nums.length == 0) return 0; 4 | let i: number = 0; 5 | for (let j: number = 1; j < nums.length; j++) { 6 | if (nums[j] != nums[i]) { 7 | i++; 8 | nums[i] = nums[j]; 9 | } 10 | } 11 | return i + 1; 12 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/array/intersectiontwoarrays.ts: -------------------------------------------------------------------------------- 1 | // Intersection of Two Arrays II 2 | function intersect(nums1: number[], nums2: number[]): number[] { 3 | nums1.sort((a, b) => a - b) 4 | nums2.sort((a, b) => a - b) 5 | let list: number[] = []; 6 | let p1: number = 0; 7 | let p2: number = 0; 8 | while (p1 < nums1.length && p2 < nums2.length) { 9 | if (nums1[p1] < nums2[p2]) { 10 | p1++; 11 | } else if (nums1[p1] > nums2[p2]) { 12 | p2++; 13 | } else { 14 | list.push(nums1[p1]); 15 | p1++; 16 | p2++; 17 | } 18 | } 19 | 20 | const result: number[] = []; 21 | let i: number = 0; 22 | while (i < list.length) { 23 | result[i] = list[i]; 24 | i++; 25 | } 26 | return result; 27 | }; 28 | -------------------------------------------------------------------------------- /top-interview-questions-easy/array/movezeroes.ts: -------------------------------------------------------------------------------- 1 | // Move Zeros 2 | function moveZeroes(nums: number[]): void { 3 | let i: number = 0; 4 | let j: number = 0; 5 | while (j < nums.length) { 6 | if (nums[j] != 0) { 7 | [nums[i], nums[j]] = [nums[j], nums[i]]; 8 | i++; 9 | } 10 | j++; 11 | } 12 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/array/plusone.ts: -------------------------------------------------------------------------------- 1 | // Plus One 2 | function plusOne(digits: number[]): number[] { 3 | for (let i = digits.length - 1; i >= 0; i--) { 4 | if (digits[i] !== 9) { 5 | digits[i]++; 6 | return digits; 7 | } else { 8 | digits[i] = 0; 9 | } 10 | } 11 | 12 | digits.unshift(1); 13 | return digits; 14 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/array/rotatearray.ts: -------------------------------------------------------------------------------- 1 | // Rotate Array 2 | function rotate(nums: number[], k: number): number[] { 3 | let a: number | undefined; 4 | for (let i = 0; i < k; i++) { 5 | a = nums.pop() 6 | if (a != undefined) 7 | nums.unshift(a); 8 | else 9 | break; 10 | } 11 | return nums; 12 | } -------------------------------------------------------------------------------- /top-interview-questions-easy/array/rotateimage.ts: -------------------------------------------------------------------------------- 1 | // Rotate Array 2 | function rotate(matrix: number[][]): void { 3 | for (let i: number = 0; i < matrix.length; i++) { 4 | for (let j: number = i; j < matrix[0].length; j++) { 5 | let temp: number = matrix[i][j]; 6 | matrix[i][j] = matrix[j][i]; 7 | matrix[j][i] = temp; 8 | } 9 | } 10 | 11 | for (let i: number = 0; i < matrix.length; i++) { 12 | for (let j: number = 0; j < matrix[0].length / 2; j++) { 13 | let temp: number = matrix[i][j]; 14 | matrix[i][j] = matrix[i][matrix[0].length - j - 1]; 15 | matrix[i][matrix[0].length - j - 1] = temp; 16 | } 17 | } 18 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/array/singlenumber.ts: -------------------------------------------------------------------------------- 1 | // Single Number (Bit Manipulation) 2 | function singleNumber(nums: number[]): number { 3 | let a: number = 0; 4 | for (let i of nums) { 5 | a ^= i; 6 | } 7 | return a; 8 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/array/twosum.ts: -------------------------------------------------------------------------------- 1 | // Two Sum 2 | function twoSum(nums: number[], target: number): number[] { 3 | const map = new Map(); 4 | 5 | for (let i: number = 0; i < nums.length; i++) { 6 | if (map.has(target - nums[i])) { 7 | return [map.get(target - nums[i]), i]; 8 | } else { 9 | map.set(nums[i], i); 10 | } 11 | } 12 | return []; 13 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/array/validsudoku.ts: -------------------------------------------------------------------------------- 1 | // Valid Sudoku 2 | function isValidSudoku(board: string[][]): boolean { 3 | for (let i: number = 0; i < 9; i++) { 4 | const row = new Set(), 5 | col = new Set(), 6 | box = new Set(); 7 | 8 | for (let j: number = 0; j < 9; j++) { 9 | const _row: string = board[i][j]; 10 | const _col: string = board[j][i]; 11 | const _box: string = board[3 * Math.floor(i / 3) + Math.floor(j / 3)][3 * (i % 3) + (j % 3)] 12 | 13 | if (_row != '.') { 14 | if (row.has(_row)) return false; 15 | row.add(_row); 16 | } 17 | if (_col != '.') { 18 | if (col.has(_col)) return false; 19 | col.add(_col); 20 | } 21 | 22 | if (_box != '.') { 23 | if (box.has(_box)) return false; 24 | box.add(_box); 25 | } 26 | } 27 | } 28 | return true; 29 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/design/minstack.ts: -------------------------------------------------------------------------------- 1 | // Min Stack 2 | const MinStack = function (): void { 3 | this.elements = []; 4 | }; 5 | 6 | MinStack.prototype.push = function (x: number): void { 7 | this.elements.push({ 8 | value: x, 9 | min: this.elements.length === 0 ? x : Math.min(x, this.getMin()), 10 | }); 11 | }; 12 | 13 | MinStack.prototype.pop = function (): void { 14 | this.elements.pop(); 15 | }; 16 | 17 | MinStack.prototype.top = function (): number { 18 | return this.elements[this.elements.length - 1].value; 19 | }; 20 | 21 | MinStack.prototype.getMin = function (): number { 22 | return this.elements[this.elements.length - 1].min; 23 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/design/shuffleanarray.ts: -------------------------------------------------------------------------------- 1 | // Shuffle an Array 2 | const Solution = function (nums: number[]) { 3 | this.nums = nums; 4 | this.original = nums.slice(); 5 | }; 6 | 7 | Solution.prototype.reset = function (): number[] { 8 | return this.original; 9 | }; 10 | 11 | Solution.prototype.shuffle = function (): number[] { 12 | this.nums.sort((a, b) => { if (Math.random() > 0.5) return 1; else return -1; }); 13 | return this.nums; 14 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/dynamic-programming/besttimetobuyandsell.ts: -------------------------------------------------------------------------------- 1 | // Best Time to Buy And Sell Stock 2 | function maxProfit(prices: number[]): number { 3 | let min: number = prices[0], max = 0; 4 | 5 | for (let i: number = 1; i < prices.length; i++) { 6 | if (prices[i] - min > max) { 7 | max = prices[i] - min; 8 | } 9 | 10 | if (prices[i] < min) min = prices[i]; 11 | } 12 | 13 | return max; 14 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/dynamic-programming/climbingstairs.ts: -------------------------------------------------------------------------------- 1 | // Climbing Stairs 2 | function climbStairs(n: number): number { 3 | let prev: number = 0; 4 | let cur: number = 1; 5 | let temp: number; 6 | 7 | for (let i: number = 0; i < n; i++) { 8 | temp = prev; 9 | prev = cur; 10 | cur += temp; 11 | } 12 | return cur; 13 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/dynamic-programming/houserobber.ts: -------------------------------------------------------------------------------- 1 | // House Robber 2 | function rob(nums: number[]): number { 3 | return nums.reduce(function (p, n) { 4 | return [p[1], Math.max(p[0] + n, p[1])]; 5 | }, [0, 0])[1]; 6 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/dynamic-programming/maximumsubarray.ts: -------------------------------------------------------------------------------- 1 | // Maximum Subarray 2 | function maxSubArray(nums: number[]): number { 3 | let prev: number = 0; 4 | let max: number = -Number.MAX_VALUE; 5 | 6 | for (let i: number = 0; i < nums.length; i++) { 7 | prev = Math.max(prev + nums[i], nums[i]); 8 | max = Math.max(max, prev); 9 | } 10 | return max; 11 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/linkedlist/deletenodeinlinkedlist.ts: -------------------------------------------------------------------------------- 1 | // Delete Node in a Linked List 2 | function deleteNode(root: any): void { 3 | root.val = root.next.val; 4 | root.next = root.next.next; 5 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/linkedlist/linkedlistcycle.ts: -------------------------------------------------------------------------------- 1 | // Linked List Cycle 2 | function hasCycle(head: any | null): boolean { 3 | let p1: any = head; 4 | let p2: any = head; 5 | 6 | while (p2 && p2.next && p2.next.next) { 7 | p1 = p1.next; 8 | p2 = p2.next.next; 9 | 10 | if (p1 === p2) { 11 | return true; 12 | } 13 | } 14 | 15 | return false; 16 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/linkedlist/mergetwosortedlists.ts: -------------------------------------------------------------------------------- 1 | // Merge Two Sorted Lists 2 | function mergeTwoLists(l1: any | null, l2: any | null): any | null { 3 | let mergedHead: any = { val: -1, next: null }, 4 | crt: any = mergedHead; 5 | while (l1 && l2) { 6 | if (l1.val > l2.val) { 7 | crt.next = l2; 8 | l2 = l2.next; 9 | } else { 10 | crt.next = l1; 11 | l1 = l1.next; 12 | } 13 | crt = crt.next; 14 | } 15 | crt.next = l1 || l2; 16 | 17 | return mergedHead.next; 18 | }; 19 | 20 | 21 | -------------------------------------------------------------------------------- /top-interview-questions-easy/linkedlist/palindromelinkedlist.ts: -------------------------------------------------------------------------------- 1 | // Palindrome Linked List 2 | function isPalindrome(head: any | null): boolean { 3 | let curr: any = head; 4 | const traverse = (node: any) => { 5 | if (node === null) { 6 | return true; 7 | } 8 | const prevIsSame: any = traverse(node.next); 9 | const currIsSame: boolean = curr.val === node.val; 10 | curr = curr.next; 11 | return prevIsSame && currIsSame; 12 | } 13 | return traverse(head); 14 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/linkedlist/removenthnode.ts: -------------------------------------------------------------------------------- 1 | // Remove Nth Node From End of List 2 | function removeNthFromEnd(head: any | null, n: number): any | null { 3 | let hare: any = head, curr: any = head; 4 | while (n--) { 5 | hare = hare.next; 6 | } 7 | while (hare && hare.next) { 8 | curr = curr.next; 9 | hare = hare.next; 10 | } 11 | if (!hare) { 12 | head = head.next; 13 | } else { 14 | curr.next = curr.next ? curr.next.next : null; 15 | } 16 | return head; 17 | }; 18 | -------------------------------------------------------------------------------- /top-interview-questions-easy/linkedlist/reverselinkedlist.ts: -------------------------------------------------------------------------------- 1 | // Reverse Linked List 2 | function reverseList(head: any | null): any | null { 3 | let [prev, current]: any[] = [null, head]; 4 | while (current) { 5 | [current.next, prev, current] = [prev, current, current.next]; 6 | } 7 | return prev; 8 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/math/countprimes.ts: -------------------------------------------------------------------------------- 1 | // Count Primes 2 | function countPrimes(n: number): number { 3 | const hash: boolean[] = new Array(n).fill(true); 4 | hash[0] = false; 5 | hash[1] = false; 6 | for (let i: number = 2; i * i < n; i++) { 7 | if (hash[i]) { 8 | for (let j: number = i * i; j < n; j += i) { // p*(p+1)... 9 | hash[j] = false; 10 | } 11 | } 12 | } 13 | return hash.filter((val) => val).length; 14 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/math/fizzbuzz.ts: -------------------------------------------------------------------------------- 1 | // Fizz Buzz 2 | function fizzBuzz(n: number): string[] { 3 | return new Array(n).fill(0).map((a, i) => (++i % 3 ? '' : 'Fizz') + (i % 5 ? '' : 'Buzz') || '' + i); 4 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/math/powerofthree.ts: -------------------------------------------------------------------------------- 1 | // Power of Three 2 | function isPowerOfThree(n: number): boolean { 3 | return /^10*$/.test(n.toString(3)); 4 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/math/romantointeger.ts: -------------------------------------------------------------------------------- 1 | // Roman to Integer 2 | const symbols = { 3 | "I": 1, 4 | "V": 5, 5 | "X": 10, 6 | "L": 50, 7 | "C": 100, 8 | "D": 500, 9 | "M": 1000 10 | }; 11 | 12 | function romanToInt(s: string): number { 13 | let value: number = 0; 14 | for (let i: number = 0; i < s.length; i += 1) { 15 | symbols[s[i]] < symbols[s[i + 1]] ? value -= symbols[s[i]] : value += symbols[s[i]]; 16 | } 17 | return value; 18 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/others/hammingdistance.ts: -------------------------------------------------------------------------------- 1 | // Hamming Distance 2 | function hammingDistance(x: number, y: number): number { 3 | let value: number = x ^ y; 4 | let counter: number = 0; 5 | 6 | while (value != 0) { 7 | if (value & 1) 8 | ++counter 9 | 10 | value = value >> 1; 11 | } 12 | 13 | return counter; 14 | }; 15 | -------------------------------------------------------------------------------- /top-interview-questions-easy/others/missingnumber.ts: -------------------------------------------------------------------------------- 1 | // Missing Number 2 | function missingNumber(nums: number[]): number { 3 | const res: any[] = new Array(nums.length + 1).fill(-1); 4 | for (const num of nums) { 5 | res[num] = num; 6 | } 7 | return res.indexOf(-1); 8 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/others/numberof1bits.ts: -------------------------------------------------------------------------------- 1 | // Number of One Bits 2 | function hammingWeight(n: number): number { 3 | let sum: number = 0; 4 | 5 | while (n != 0) { 6 | sum += n & 1; 7 | n = n >>> 1; 8 | } 9 | 10 | return sum; 11 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/others/pascaltriangle.ts: -------------------------------------------------------------------------------- 1 | // Pascal's Triangle 2 | function generate(numRows: number): number[][] { 3 | const pascal: any[] = []; 4 | for (let i: number = 0; i < numRows; i++) { 5 | pascal[i] = []; 6 | pascal[i][0] = 1; 7 | for (let j: number = 1; j < i; j++) { 8 | pascal[i][j] = pascal[i - 1][j - 1] + pascal[i - 1][j] 9 | } 10 | pascal[i][i] = 1; 11 | } 12 | return pascal; 13 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/others/reversebits.ts: -------------------------------------------------------------------------------- 1 | // Reverse Bits 2 | function reverseBits(n: number): number { 3 | let result: number = 0; 4 | let count: number = 32; 5 | 6 | while (count--) { 7 | result *= 2; 8 | result += n & 1; 9 | n = n >> 1; 10 | } 11 | return result; 12 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/others/validparenthesis.ts: -------------------------------------------------------------------------------- 1 | // Valid Parenthesis 2 | function isValid(s: string): boolean { 3 | const stack: any[] = []; 4 | 5 | for (let i: number = 0; i < s.length; i++) { 6 | let c: string = s.charAt(i); 7 | switch (c) { 8 | case '(': stack.push(')'); 9 | break; 10 | case '[': stack.push(']'); 11 | break; 12 | case '{': stack.push('}'); 13 | break; 14 | default: 15 | if (c !== stack.pop()) { 16 | return false; 17 | } 18 | } 19 | } 20 | return stack.length === 0; 21 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/sorted-and-searching/firstbadversion.ts: -------------------------------------------------------------------------------- 1 | // First Bad Version 2 | const solution = function (isBadVersion: any) { 3 | 4 | return function (n: number): number { 5 | let start: number = 1, end = n; 6 | while (start < end) { 7 | const mid: number = Math.floor(start + (end - start) / 2); 8 | if (isBadVersion(mid)) { 9 | end = mid; 10 | } else { 11 | start = mid + 1; 12 | } 13 | } 14 | return start; 15 | }; 16 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/sorted-and-searching/mergesortedarray.ts: -------------------------------------------------------------------------------- 1 | // Merge Sorted Array 2 | function merge(nums1: number[], m: number, nums2: number[], n: number): void { 3 | let insertPos: number = m + n - 1; 4 | m--; n--; 5 | while (n >= 0) { 6 | nums1[insertPos--] = (nums1[m] > nums2[n]) ? nums1[m--] : nums2[n--]; 7 | } 8 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/strings/atoi.ts: -------------------------------------------------------------------------------- 1 | // String To Integer (atoi) 2 | function myAtoi(s: string): number { 3 | return Math.max(Math.min(parseInt(s) || 0, 2147483647), -2147483648) 4 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/strings/countandsay.ts: -------------------------------------------------------------------------------- 1 | // Count and Say 2 | function countAndSay(n: number): string { 3 | let str: string = '1'; 4 | for (let i: number = 1; i < n; i++) { 5 | let strArray: string[] = str.split(''); 6 | str = ''; 7 | let count: number = 1; 8 | for (let j: number = 0; j < strArray.length; j++) { 9 | if (strArray[j] !== strArray[j + 1]) { 10 | str += count + strArray[j]; 11 | count = 1; 12 | } 13 | else { 14 | count++; 15 | } 16 | } 17 | } 18 | return str; 19 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/strings/firstuniquechar.ts: -------------------------------------------------------------------------------- 1 | // First Unique Character in a String 2 | function firstUniqChar(s: string): number { 3 | for (let i: number = 0; i < s.length; i++) 4 | if (s.indexOf(s[i]) === s.lastIndexOf(s[i])) return i; 5 | return -1; 6 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/strings/longestcommonprefix.ts: -------------------------------------------------------------------------------- 1 | // Longest Common Prefix 2 | function longestCommonPrefix(strs: string[]): string { 3 | if (strs === undefined || strs.length === 0) { return ''; } 4 | 5 | return strs.reduce((prev, next) => { 6 | let i: number = 0; 7 | while (prev[i] && next[i] && prev[i] === next[i]) i++; 8 | return prev.slice(0, i); 9 | }); 10 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/strings/reverseinteger.ts: -------------------------------------------------------------------------------- 1 | // Reverse Integer 2 | function reverse(x: number): number { 3 | const absReversed: any = Math.abs(x).toString().split('').reverse().join(''); 4 | if (absReversed > 2 ** 31) return 0; 5 | return absReversed * Math.sign(x); 6 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/strings/reversestring.ts: -------------------------------------------------------------------------------- 1 | // Reverse String 2 | function reverseString(s: string[]): void { 3 | let i: number = 0, j: number = s.length - 1; 4 | while (i < j) { 5 | [s[i], s[j]] = [s[j], s[i]]; 6 | i++; 7 | j--; 8 | } 9 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/strings/strStr.ts: -------------------------------------------------------------------------------- 1 | // Implement strStr() 2 | function strStr(haystack: string, needle: string): number { 3 | const needleLength: number = needle.length; 4 | if (needleLength === 0) return 0; 5 | for (let i: number = 0; i < haystack.length; i++) { 6 | if (haystack.substring(i, i + needleLength) === needle) { 7 | return i; 8 | } 9 | } 10 | return -1; 11 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/strings/validanagram.ts: -------------------------------------------------------------------------------- 1 | // Valid Anagram 2 | function isAnagram(s: string, t: string): boolean { 3 | const map: any = {}; 4 | s.split('').map(c => map[c] = map[c] ? map[c] + 1 : 1); 5 | t.split('').map(c => map[c] = map[c] ? map[c] - 1 : -1); 6 | return Object.keys(map).every(k => map[k] === 0); 7 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/strings/validpalindrome.ts: -------------------------------------------------------------------------------- 1 | // Valid Palindrome 2 | function isPalindrome(s: string): boolean { 3 | s = s.toLowerCase().replace(/[^a-z0-9]/gi, ''); 4 | for (let i: number = 0, j = s.length - 1; i <= j; i++, j--) { 5 | if (s.charAt(i) !== s.charAt(j)) return false; 6 | } 7 | return true; 8 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/trees/binarytreelevelordertraversal.ts: -------------------------------------------------------------------------------- 1 | // Binary Tree Level Order Traversal 2 | function levelOrder(root: any | null): number[][] { 3 | if (!root) return []; 4 | 5 | const queue: any[] = [root]; 6 | const levels: any[] = []; 7 | 8 | while (queue.length !== 0) { 9 | const queueLength: number = queue.length; 10 | const currLevel: any[] = []; 11 | for (let i: number = 0; i < queueLength; i++) { 12 | const current: any = queue.shift(); 13 | if (current.left) { 14 | queue.push(current.left); 15 | } 16 | if (current.right) { 17 | queue.push(current.right); 18 | } 19 | currLevel.push(current.val); 20 | } 21 | levels.push(currLevel); 22 | } 23 | return levels; 24 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/trees/convertsortedarraytotree.ts: -------------------------------------------------------------------------------- 1 | // Convert Sorted Array to Binary Search Tree 2 | function sortedArrayToBST(nums: number[]): TreeNode | null { 3 | if (!nums.length) return null; 4 | 5 | const mid: number = Math.floor(nums.length / 2); 6 | const root: TreeNode = new TreeNode(nums[mid]); 7 | 8 | // subtrees are BSTs as well 9 | root.left = sortedArrayToBST(nums.slice(0, mid)); 10 | root.right = sortedArrayToBST(nums.slice(mid + 1)); 11 | 12 | return root; 13 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/trees/maxdepthofbinarytree.ts: -------------------------------------------------------------------------------- 1 | // Maximum Depth of Binary Tree 2 | function maxDepth(root: TreeNode | null): number { 3 | if (root === undefined || root === null) { 4 | return 0; 5 | } 6 | return Math.max(maxDepth(root.left), maxDepth(root.right)) + 1; 7 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/trees/ordertraversal.ts: -------------------------------------------------------------------------------- 1 | // Binary Tree Level Order Traversal 2 | function levelOrder(root: TreeNode | null): number[][] { 3 | const stack: any[] = []; 4 | const res: any[] = []; 5 | 6 | while (root || stack.length) { 7 | if (root) { 8 | stack.push(root); 9 | root = root.left; 10 | } else { 11 | root = stack.pop(); 12 | res.push(root.val); 13 | root = root.right; 14 | } 15 | } 16 | 17 | return res; 18 | }; 19 | -------------------------------------------------------------------------------- /top-interview-questions-easy/trees/symmetrictree.ts: -------------------------------------------------------------------------------- 1 | // Symmetric Tree 2 | function isSymmetric(root: TreeNode | null): boolean { 3 | if (!root) return true; 4 | let leftArr: any[] = [root.left], rightArr = [root.right]; 5 | while (leftArr.length && rightArr.length) { 6 | let l: any = leftArr.pop(), r: any = rightArr.pop(); 7 | if (!l && !r) continue; 8 | if (!l || !r) return false; 9 | if (l.val !== r.val) return false; 10 | leftArr.push(l && l.left); 11 | leftArr.push(l && l.right); 12 | rightArr.push(r && r.right); 13 | rightArr.push(r && r.left); 14 | } 15 | return true; 16 | }; -------------------------------------------------------------------------------- /top-interview-questions-easy/trees/validatebinarysearchtree.ts: -------------------------------------------------------------------------------- 1 | // Validate Binary Search Tree 2 | function isValidBST(root: any | null, min = -Infinity, max = Infinity): boolean { 3 | if (!root) return true; 4 | return !(root.val <= min || root.val >= max) && isValidBST(root.left, min, root.val) && isValidBST(root.right, root.val, max); 5 | }; --------------------------------------------------------------------------------