ds-algo-study

<html> <head> <meta http-equiv=Content-Type content="text/html; charset=windows-1252"> <meta name=Generator content="Microsoft Word 15 (filtered)"> <style>  </style> </head> <body lang=EN-US link=blue vlink="#954F72" style='word-wrap:break-word'> <div class=WordSection1> Heaps Project This project contains a skeleton for you to implement a max heap. This is a test-driven project. Run the tests and read the top-most error. If it's not clear what is failing, open the test/test.js file to figure out what the test is expecting. Make the top-most test pass. Keep making the top-most test pass until all tests pass. <div style='border:none;border-bottom:solid #DDDDDD 1.0pt;padding:0in 0in 4.0pt 0in; background:white'> Instructions </div> �    cd into the project folder �    npm install to install dependencies in the project root directory �    npm test to run the specs �    You can view the test cases in test/test.js. Your job is to write code in o    lib/max_heap.js to implement the MaxHeap class o    lib/is_heap.js to implement the isMaxHeap function o    lib/leet_code_215.js to implement the findKthLargest function located at <a href="https://leetcode.com/problems/kth-largest-element-in-an-array/" target="_blank">https://leetcode.com/problems/kth-largest-element-in-an-array/</a>             <img width=852 height=384 src="Heaps-project_files/image001.png" alt="Graphical user interface, application, Teams

Description automatically generated">                          /** �* @param {number[]} nums �* @param {number} k �* @return {number} �*/ let findKthLargest = function(nums, k) { �� };       Soln:-------------------------------------------------------------- // you may assume that the array will always have a null element at the 0-th index   function isMaxHeap( array ) {     // check if the tree is complete, i.e. there are no gaps like [null, 50, undefined, 20]     let isComplete = array.every( el => el !== undefined );     return isComplete && _isMaxHeap( array ); }   function _isMaxHeap( array, idx = 1 ) {     if ( array[ idx ] === undefined ) return true;     let leftIdx = 2 * idx;     let rightIdx = 2 * idx + 1;     let leftVal;       if ( array[ leftIdx ] === undefined ) {         leftVal = -Infinity;     } else {         leftVal = array[ leftIdx ];     }       let rightVal;       if ( array[ rightIdx ] === undefined ) {         rightVal = -Infinity;     } else {         rightVal = array[ rightIdx ];     }       return array[ idx ] > leftVal && array[ idx ] > rightVal &&         _isMaxHeap( array, leftIdx ) && _isMaxHeap( array, rightIdx ); }   module.exports = {     isMaxHeap };   -------------------------------------------------------------------------------------------------------- class MaxHeap {     constructor() {         this.array = [null];     }       getParent(idx) {         return Math.floor(idx / 2);     }       getLeftChild(idx) {         return idx * 2;     }       getRightChild(idx) {         return idx * 2 + 1;     }       insert(val) {         this.array.push(val);         this.siftUp(this.array.length - 1);     }          siftUp(idx) {         if (idx === 1) return;                  let parentIdx = this.getParent(idx);           if (this.array[parentIdx] < this.array[idx]) {             [ this.array[parentIdx], this.array[idx] ] = [ this.array[idx], this.array[parentIdx] ];             this.siftUp(parentIdx);         }     }       deleteMax() {         if (this.array.length === 2) return this.array.pop();         if (this.array.length === 1) return null;           let max = this.array[1];         this.array[1] = this.array.pop();         this.siftDown(1);         return max;     }       siftDown(idx) {         let ary = this.array;         let leftIdx = this.getLeftChild(idx);         let rightIdx = this.getRightChild(idx);          let leftVal = ary[leftIdx];         let rightVal = ary[rightIdx];           if (leftVal === undefined) leftVal = -Infinity;         if (rightVal === undefined) rightVal = -Infinity;              if (ary[idx] > leftVal && ary[idx] > rightVal) return;              if (leftVal < rightVal) {           var swapIdx = rightIdx;         } else {           var swapIdx = leftIdx;         }              [ ary[idx], ary[swapIdx] ] = [ ary[swapIdx], ary[idx] ];         this.siftDown(swapIdx);     } }   module.exports = {     MaxHeap };   </div> </body> </html>