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[alexgoni] 24.11.26 (#108)
* 56 / Merge Intervals / Medium / 30m * 1584 / Min Cost to Connect All Points / Medium * 235 / Lowest Common Ancestor of a Binary Search Tree / Medium * 139 / Word Break / Medium * 215 / Kth Largest Element in an Array / Medium
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‎alexgoni/102_Binary_Tree_Level_Order_Traversal.js‎

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// 😢
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/**
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* Definition for a binary tree node.
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* function TreeNode(val, left, right) {
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* this.val = (val===undefined ? 0 : val)
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* this.left = (left===undefined ? null : left)
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* this.right = (right===undefined ? null : right)
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* }
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*/
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/**
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* @param {TreeNode} root
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* @return {number[][]}
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*/
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var levelOrder = function (root) {
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if (!root) return [];
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const result = [];
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const q = [root];
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while (q.length > 0) {
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const level = [];
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const size = q.length;
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for (let i = 0; i < size; i++) {
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const node = q.shift();
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level.push(node.val);
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if (node.left) q.push(node.left);
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if (node.right) q.push(node.right);
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}
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result.push(level);
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}
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return result;
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};

‎alexgoni/139_Word_Break.js‎

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// 😢
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/**
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* @param {string} s
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* @param {string[]} wordDict
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* @return {boolean}
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*/
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var wordBreak = function (s, wordDict) {
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const wordSet = new Set(wordDict);
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const dp = Array.from({ length: s.length + 1 }).fill(false);
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dp[0] = true;
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for (let i = 1; i <= s.length; i++) {
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for (let j = 0; j < i; j++) {
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if (dp[j] && wordSet.has(s.slice(j, i))) {
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dp[i] = true;
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break;
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}
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}
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}
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return dp[s.length];
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};

‎alexgoni/150_Evaluate_Reverse_Polish_Notation.js‎

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// /**
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// * @param {string[]} tokens
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// * @return {number}
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// */
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// var evalRPN = function(tokens) {
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// let i = 0;
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// while(tokens.length > 1) {
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// if(isNaN(tokens[i])) {
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// let temp;
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// if(tokens[i] === "+") temp = Number(tokens[i-2]) + Number(tokens[i-1]);
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// if(tokens[i] === "-") temp = Number(tokens[i-2]) - Number(tokens[i-1]);
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// if(tokens[i] === "*") temp = Number(tokens[i-2]) * Number(tokens[i-1]);
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// if(tokens[i] === "/") temp = Math.trunc(Number(tokens[i-2]) / Number(tokens[i-1]));
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// tokens.splice(i-2, 3, temp);
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// i = 0;
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// }
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// i++;
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// }
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// return +tokens[0];
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// };
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/**
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* @param {string[]} tokens
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* @return {number}
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*/
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var evalRPN = function (tokens) {
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const stack = [];
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for (let token of tokens) {
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if (!isNaN(token)) stack.push(Number(token));
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else {
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const b = stack.pop();
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const a = stack.pop();
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if (token === "+") stack.push(a + b);
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if (token === "-") stack.push(a - b);
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if (token === "*") stack.push(a * b);
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if (token === "/") stack.push(Math.trunc(a / b));
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}
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}
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return stack.pop();
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};

‎alexgoni/1584_Min_Cost_to_Connect_All_Points.js‎

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// 😢
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/**
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* @param {number[][]} points
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* @return {number}
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*/
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var minCostConnectPoints = function (points) {
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const n = points.length;
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const visited = Array(n).fill(false);
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const minDist = Array(n).fill(Infinity);
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minDist[0] = 0;
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let result = 0;
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for (let i = 0; i < n; i++) {
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let currMin = Infinity;
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let currNode = -1;
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for (let j = 0; j < n; j++) {
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if (!visited[j] && minDist[j] < currMin) {
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currMin = minDist[j];
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currNode = j;
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}
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}
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visited[currNode] = true;
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result += currMin;
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for (let j = 0; j < n; j++) {
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if (!visited[j]) {
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const cost =
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Math.abs(points[currNode][0] - points[j][0]) +
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Math.abs(points[currNode][1] - points[j][1]);
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minDist[j] = Math.min(minDist[j], cost);
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}
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}
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}
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return result;
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};

‎alexgoni/207_Course_Schedule.js‎

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// 😢
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/**
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* @param {number} numCourses
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* @param {number[][]} prerequisites
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* @return {boolean}
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*/
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var canFinish = function (numCourses, prerequisites) {
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const graph = Array.from({ length: numCourses }, () => []);
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for (const [a, b] of prerequisites) {
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graph[b].push(a);
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}
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const visited = Array(numCourses).fill(0);
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const hasCycle = (cource) => {
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if (visited[cource] === 1) return true;
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if (visited[cource] === 2) return false;
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visited[cource] = 1;
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for (const neighbor of graph[cource]) {
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if (hasCycle(neighbor)) return true;
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}
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visited[cource] = 2;
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return false;
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};
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for (let i = 0; i < numCourses; i++) {
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if (hasCycle(i)) return false;
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}
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return true;
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};

‎alexgoni/213_House_Robber_ll.js‎

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/**
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* @param {number[]} nums
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* @return {number}
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*/
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var rob = function (nums) {
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if (nums.length <= 3) return Math.max(...nums);
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const firstNums = nums.slice(0, nums.length - 1);
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const secondNums = nums.slice(1);
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const firstDp = [firstNums[0], firstNums[1]];
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const secondDp = [secondNums[0], secondNums[1]];
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for (let i = 2; i < firstNums.length; i++) {
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if (i === 2) firstDp[i] = firstDp[0] + firstNums[i];
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else firstDp[i] = Math.max(firstDp[i - 2], firstDp[i - 3]) + firstNums[i];
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}
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for (let i = 2; i < secondNums.length; i++) {
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if (i === 2) secondDp[i] = secondDp[0] + secondNums[i];
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else
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secondDp[i] = Math.max(secondDp[i - 2], secondDp[i - 3]) + secondNums[i];
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}
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return Math.max(
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firstDp[firstNums.length - 1],
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firstDp[firstNums.length - 2],
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secondDp[secondNums.length - 1],
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secondDp[secondNums.length - 2]
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);
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};

‎alexgoni/215_Kth_Largest_Element_in_an_Array.js‎

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// 😢
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/**
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* @param {number[]} nums
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* @param {number} k
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* @return {number}
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*/
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var findKthLargest = function (nums, k) {
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const heap = new MaxBinaryHeap();
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for (const num of nums) {
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heap.insert(num);
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}
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for (let i = 0; i < k; i++) {
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const extractedValue = heap.extractMax();
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if (i === k - 1) return extractedValue;
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}
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};
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class MaxBinaryHeap {
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constructor() {
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this.values = [];
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}
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insert(value) {
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this.values.push(value);
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this.#bubbleUp();
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return this.values;
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}
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extractMax() {
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const extractedValue = this.values[0];
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const poppedValue = this.values.pop();
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if (this.values.length === 0) return extractedValue;
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this.values[0] = poppedValue;
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this.#sinkDown();
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return extractedValue;
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}
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#bubbleUp() {
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let currentIndex = this.values.length - 1;
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const currentValue = this.values[currentIndex];
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while (currentIndex > 0) {
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const parentIndex = Math.floor((currentIndex - 1) / 2);
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const parentValue = this.values[parentIndex];
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if (parentValue >= currentValue) break;
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this.values[parentIndex] = currentValue;
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this.values[currentIndex] = parentValue;
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currentIndex = parentIndex;
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}
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}
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#sinkDown() {
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let currentIndex = 0;
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const currentValue = this.values[currentIndex];
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const length = this.values.length;
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while (true) {
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let leftChildIndex = currentIndex * 2 + 1;
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let rightChildIndex = currentIndex * 2 + 2;
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let leftChildValue, rightChildValue;
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let swapWith = null;
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if (leftChildIndex < length) {
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leftChildValue = this.values[leftChildIndex];
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if (leftChildValue > currentValue) swapWith = leftChildIndex;
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}
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if (rightChildIndex < length) {
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rightChildValue = this.values[rightChildIndex];
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if (
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(!swapWith && rightChildValue > currentValue) ||
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(swapWith && rightChildValue > leftChildValue)
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) {
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swapWith = rightChildIndex;
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}
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}
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if (!swapWith) break;
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this.values[currentIndex] = this.values[swapWith];
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this.values[swapWith] = currentValue;
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currentIndex = swapWith;
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}
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}
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}

‎alexgoni/235_Lowest_Common_Ancestor_of_a_Binary_Search_Tree.js‎

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// 😢
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/**
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* Definition for a binary tree node.
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* function TreeNode(val) {
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* this.val = val;
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* this.left = this.right = null;
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* }
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*/
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/**
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* @param {TreeNode} root
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* @param {TreeNode} p
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* @param {TreeNode} q
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* @return {TreeNode}
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*/
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var lowestCommonAncestor = function (root, p, q) {
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if (p.val < root.val && q.val < root.val) {
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return lowestCommonAncestor(root.left, p, q);
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}
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if (p.val > root.val && q.val > root.val) {
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return lowestCommonAncestor(root.right, p, q);
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}
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return root;
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};

‎alexgoni/56_Merge_Intervals.js‎

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/**
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* @param {number[][]} intervals
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* @return {number[][]}
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*/
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var merge = function (intervals) {
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const result = [];
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intervals.sort((a, b) => a[0] - b[0]);
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let i = 0;
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while (i < intervals.length - 1) {
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if (intervals[i][1] >= intervals[i + 1][0]) {
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intervals.splice(i, 2, [
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intervals[i][0],
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Math.max(intervals[i][1], intervals[i + 1][1]),
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]);
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} else {
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i++;
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}
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}
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return intervals;
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};

‎alexgoni/572_Subtree_of_Another_Tree.js‎

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/**
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* Definition for a binary tree node.
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* function TreeNode(val, left, right) {
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* this.val = (val===undefined ? 0 : val)
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* this.left = (left===undefined ? null : left)
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* this.right = (right===undefined ? null : right)
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* }
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*/
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/**
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* @param {TreeNode} root
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* @param {TreeNode} subRoot
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* @return {boolean}
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*/
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var isSubtree = function (root, subRoot) {
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if (!root) return false;
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if (isSameTree(root, subRoot)) return true;
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return isSubtree(root.left, subRoot) || isSubtree(root.right, subRoot);
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};
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function isSameTree(root1, root2) {
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if (!root1 && !root2) return true;
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if (!root1 || !root2) return false;
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if (root1.val !== root2.val) return false;
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return (
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isSameTree(root1.left, root2.left) && isSameTree(root1.right, root2.right)
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);
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}

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