Last active
May 24, 2020 20:10
-
-
Save wovalle/a86a76bc20d8c886342040f54875f291 to your computer and use it in GitHub Desktop.
LeetCode May 2020
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
// LeetCode May 2020 |
Author
wovalle
commented
May 12, 2020
•
// 13.js
/**
* @param {string} num
* @param {number} k
* @return {string}
*/
var removeKdigits = function(num, k) {
let answer = num
for(let times = 0; times < k; times++) {
let wasSet = false
for(let i = 0; i < answer.length - 1; i++) {
if (answer[i] > answer[i+1]) {
answer = answer.slice(0, i) + answer.slice(i + 1)
wasSet = true
break
}
}
if(!wasSet) {
answer = answer.slice(0, -1)
}
}
const indexOfNonZero = answer.search(/[1-9]/)
return indexOfNonZero === -1 ? "0" : answer.slice(indexOfNonZero)
};
// Time: O(n)
// Space: O(n) //can be done in-place, didn't want to destroy the input
// 14.js
class Node {
constructor(val) {
this.children = new Map()
this.isFinalWord = false
}
}
class Trie {
constructor() {
this.root = new Node('*')
}
insert = (word) => {
let node = this.root
let index = 0
while (node.children.get(word[index]) && index < word.length) {
node = node.children.get(word[index])
index++
}
while (word.length > index) {
const currentNode = new Node()
node.children.set(word[index], currentNode)
node = currentNode
index++
}
node.isFinalWord = true
};
search = (word) => {
let node = this.root
for (let letter of word) {
node = node.children.get(letter)
if (!node) {
return false
}
}
return node.isFinalWord
};
startsWith = (prefix) => {
let node = this.root
for (let letter of prefix) {
node = node.children.get(letter)
if (!node) {
return false
}
}
return true
};
}
// Time: O(n) (where n is word.length)
// Space: O(n)
//15.js
/**
* @param {number[]} A
* @return {number}
*/
const maxKadane = (arr) => {
let max = 0
let maxSoFar = 0
for (let i = 0; i < arr.length; i++) {
maxSoFar = Math.max(maxSoFar + arr[i], 0)
max = Math.max(max, maxSoFar)
}
return max
}
var maxSubarraySumCircular = function (A) {
// First, get the max subarray sum
const maxSingle = maxKadane(A)
// If it returned 0 it means that all numbers are negative, just return the max out of them
if (maxSingle === 0) {
return Math.max(...A)
}
const maxNegated = maxKadane(A.map(e => e * -1))
const sum = A.reduce((acc, cur) => acc += cur)
return Math.max(maxSingle, sum + maxNegated)
};
// Time: O(n)
// Space: O(n)
// 16.js
/**
* Definition for singly-linked list.
* function ListNode(val, next) {
* this.val = (val===undefined ? 0 : val)
* this.next = (next===undefined ? null : next)
* }
*/
/**
* @param {ListNode} head
* @return {ListNode}
*/
var oddEvenList = function(head) {
if(!head) return null
let [node, nextEven, evens] = [head, head.next, head.next]
while(nextEven !== null && nextEven.next !== null) {
node.next = node.next.next
node = node.next
nextEven.next = node.next
nextEven = nextEven.next
}
node.next = evens
return head
};
// Time: O(n)
// Space: O(1) (I'm just saving the references for the even nodes)
// 17.js
const getCode = (s, i) => s.charCodeAt(i) - 'a'.charCodeAt(0);
const areEqualArrays = (a1, a2) => {
for (let i = 0; i <= a1.length; i++) {
if (a1[i] !== a2[i]) {
return false;
}
}
return true;
};
const findAnagrams = (p, s) => {
const freqS = new Array(26).fill(0);
const freqP = new Array(26).fill(0);
const answer = [];
for (let i = 0; i < s.length; i++) {
freqS[getCode(s, i)]++;
}
for (let i = 0; i < s.length; i++) {
freqP[getCode(p, i)]++;
}
for (let i = s.length; i < p.length; i++) {
if (areEqualArrays(freqS, freqP)) {
answer.push(i - s.length);
}
freqP[getCode(p, i)]++;
freqP[getCode(p, i - s.length)]--;
}
if (areEqualArrays(freqS, freqP)) {
answer.push(p.length - s.length);
}
return answer;
};
// Time: O(S + P) = O(n)
// Space: O(1)
// 18.js
var checkInclusion = function (s1, s2) {
if (s1.length > s2.length) {
return false;
}
const freq = new Array(26).fill(0);
const base = 'a'.charCodeAt(0);
const getCode = (s, i) => s.charCodeAt(i) - base;
const areEqualArrays = (a1, a2) => {
for (let i = 0; i <= a1.length; i++) {
if (a1[i] !== a2[i]) {
return false;
}
}
return true;
};
for (let i = 0; i < s1.length; i++) {
freq[getCode(s1, i)]++;
}
for (let i = 0; i < s2.length; i++) {
if (freq[getCode(s2, i)] > 0) {
const currentFreq = new Array(26).fill(0);
for (let j = i; j < s2.length; j++) {
const currentCode = getCode(s2, j);
currentFreq[currentCode]++;
// if we find another character before length, just discard the positions
if (freq[currentCode] === 0) {
i = j;
break;
}
if (j - i < s1.length - 1) {
continue;
}
if (areEqualArrays(freq, currentFreq)) {
return true;
} else {
currentFreq[getCode(s2, j - s1.length + 1)]--;
}
}
}
}
return false;
};
// Time: O(n)
// Space: O(n)
// 19.js
class StockSpanner {
max = -Infinity;
maxCount = 0;
localMax = [];
next(stock) {
const peek = (arr) => arr[arr.length - 1];
if (stock >= this.max) {
this.max = stock;
const localMax = this.localMax.length
? this.localMax.reduce((acc, cur) => (acc += cur[1]), 0)
: 0;
this.maxCount = this.maxCount + localMax + 1;
this.localMax = [];
return this.maxCount;
}
let localCount = 1;
while (this.localMax.length && stock >= peek(this.localMax)[0]) {
const [_, count] = this.localMax.pop();
localCount += count;
}
this.localMax.push([stock, localCount]);
return localCount;
}
}
// Time: O(n)
// Space: O(n)
// 20.js
var kthSmallest = function (root, k) {
let stack = [root];
let node = root;
while (stack.length) {
while (node) {
stack.push(node);
node = node.left;
}
node = stack.pop();
if (k === 1) {
return node.val;
} else {
k--;
}
node = node.right;
}
return null;
};
// Time: O(n)
// Space: O(n)
// 21.js
/**
* @param {number[][]} matrix
* @return {number}
*/
const isValidSubMatrix = (matrix, x, y, side) => {
if (y + side > matrix.length || x + side > matrix[y].length) {
return false;
}
if (side === 1) {
return matrix[y][x] === 1;
}
for (let sy = y; sy < y + side; sy++) {
for (let sx = x; sx < x + side; sx++) {
if (!matrix[sy][sx]) {
return false;
}
}
}
return true;
};
var countSquares = function (matrix) {
const times = Math.min(matrix.length, matrix[0].length);
let number = 0;
for (let side = 1; side <= times; side++) {
for (let y = 0; y < matrix.length; y++) {
for (let x = 0; x < matrix[y].length; x++) {
if (isValidSubMatrix(matrix, x, y, side)) {
number++;
}
}
}
}
return number;
};
// Time: O(n ^ 3) or O(n ^ 4), lol
// Space: O(1)
// 22.js
/**
* @param {string} s
* @return {string}
*/
var frequencySort = function(s) {
// It would be nice if we had some type of ordered Map
// to prevent the sort in line 15
const freq = {}
for (let letter of s) {
freq[letter] = (freq[letter] || 0) + 1
}
return Object.entries(freq)
.sort((a, b) => b[1] - a[1])
.map(e => e[0].repeat(e[1]))
.join('')
};
// Time: O(n)
// Space: O(n)
// 23.js
/**
* @param {number[][]} A
* @param {number[][]} B
* @return {number[][]}
*/
var intervalIntersection = function(A, B) {
const getIntersection = (a, b) => {
if (a[1] < b[0] || a[0] > b[1])
return null
return [Math.max(a[0], b[0]), Math.min(a[1], b[1])]
}
let pivotA = 0
let pivotB = 0
const answer = []
while (pivotA < A.length && pivotB < B.length) {
const intersection = getIntersection(A[pivotA], B[pivotB])
if(intersection) {
answer.push(intersection)
}
if(A[pivotA][1] < B[pivotB][1]) {
pivotA++
} else {
pivotB++
}
}
return answer
};
// Time: O(A + B) = O(n)
// Space: O(N)
// 24.js
const getLast = (arr, level = 1) => (arr.length ? arr[arr.length - level] : null);
const bstFromPreorder = function (preorder) {
if (!preorder.length) {
return null;
}
const leaves = [[new TreeNode(preorder.shift()), -Infinity, Infinity]];
while (preorder.length) {
const currentVal = preorder.shift();
while (currentVal > getLast(leaves)[2] || currentVal < getLast(leaves)[1]) {
leaves.pop();
}
const [leave, min, max] = getLast(leaves);
if (currentVal > leave.val) {
leave.right = new TreeNode(currentVal);
leaves.push([leave.right, leave.val, max]);
} else if (currentVal < leave.val) {
leave.left = new TreeNode(currentVal);
leaves.push([leave.left, min, leave.val]);
}
}
return leaves[0][0];
};
// Time: O(n)
// Space: O(n)
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment