Add heap part js code (#339)
* Add heap part js code * Update heap.md * Update heap.md * Format the code style and fix a bug. * and fix the style in heap.md * fix the style --------- Co-authored-by: Yudong Jin <krahets@163.com>pull/358/head
Leo.Cai
2 years ago
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/**
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* File: my_heap.js
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* Created Time: 2023-02-06
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* Author: what-is-me (whatisme@outlook.jp)
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*/
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const { printHeap } = require("../include/PrintUtil");
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/* 最大堆类 */
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class MaxHeap {
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#maxHeap;
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/* 构造函数，建立空堆或根据输入列表建堆 */
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constructor(nums) {
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// 将列表元素原封不动添加进堆
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this.#maxHeap = nums === undefined ? [] : [...nums];
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// 堆化除叶结点以外的其他所有结点
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for (let i = this.#parent(this.size() - 1); i >= 0; i--) {
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this.#siftDown(i);
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}
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}
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/* 获取左子结点索引 */
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#left(i) {
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return 2 * i + 1;
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}
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/* 获取右子结点索引 */
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#right(i) {
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return 2 * i + 2;
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}
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/* 获取父结点索引 */
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#parent(i) {
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return Math.floor((i - 1) / 2); // 向下整除
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}
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/* 交换元素 */
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#swap(i, j) {
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const a = this.#maxHeap[i],
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b = this.#maxHeap[j],
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tmp = a;
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this.#maxHeap[i] = b;
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this.#maxHeap[j] = tmp;
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}
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/* 获取堆大小 */
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size() {
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return this.#maxHeap.length;
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}
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/* 判断堆是否为空 */
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isEmpty() {
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return this.size() === 0;
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}
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/* 访问堆顶元素 */
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peek() {
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return this.#maxHeap[0];
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}
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/* 元素入堆 */
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push(val) {
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// 添加结点
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this.#maxHeap.push(val);
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// 从底至顶堆化
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this.#siftUp(this.size() - 1);
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}
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/* 从结点 i 开始，从底至顶堆化 */
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#siftUp(i) {
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while (true) {
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// 获取结点 i 的父结点
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const p = this.#parent(i);
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// 当“越过根结点”或“结点无需修复”时，结束堆化
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if (p < 0 || this.#maxHeap[i] <= this.#maxHeap[p]) break;
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// 交换两结点
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this.#swap(i, p);
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// 循环向上堆化
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i = p;
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}
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}
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/* 元素出堆 */
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poll() {
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// 判空处理
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if (this.isEmpty()) throw new Error("堆为空");
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// 交换根结点与最右叶结点（即交换首元素与尾元素）
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this.#swap(0, this.size() - 1);
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// 删除结点
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const val = this.#maxHeap.pop();
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// 从顶至底堆化
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this.#siftDown(0);
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// 返回堆顶元素
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return val;
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}
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/* 从结点 i 开始，从顶至底堆化 */
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#siftDown(i) {
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while (true) {
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// 判断结点 i, l, r 中值最大的结点，记为 ma
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const l = this.#left(i),
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r = this.#right(i);
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let ma = i;
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if (l < this.size() && this.#maxHeap[l] > this.#maxHeap[ma]) ma = l;
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if (r < this.size() && this.#maxHeap[r] > this.#maxHeap[ma]) ma = r;
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// 若结点 i 最大或索引 l, r 越界，则无需继续堆化，跳出
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if (ma == i) break;
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// 交换两结点
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this.#swap(i, ma);
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// 循环向下堆化
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i = ma;
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}
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}
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/* 打印堆（二叉树） */
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print() {
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printHeap(this.#maxHeap);
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}
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}
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function testPush(maxHeap, val) {
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maxHeap.push(val); // 元素入堆
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console.log(`\n添加元素 ${val} 后`);
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maxHeap.print();
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}
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function testPoll(maxHeap) {
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let val = maxHeap.poll(); // 堆顶元素出堆
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console.log(`\n出堆元素为 ${val}`);
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maxHeap.print();
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}
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/* 初始化大顶堆 */
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const maxHeap = new MaxHeap([9, 8, 6, 6, 7, 5, 2, 1, 4, 3, 6, 2]);
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console.log("\n输入列表并建堆后");
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maxHeap.print();
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/* 获取堆顶元素 */
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let peek = maxHeap.peek();
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console.log(`\n堆顶元素为 ${peek}`);
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/* 元素入堆 */
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let val = 7;
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maxHeap.push(val);
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console.log(`\n元素 ${val} 入堆后`);
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maxHeap.print();
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/* 堆顶元素出堆 */
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peek = maxHeap.poll();
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console.log(`\n堆顶元素 ${peek} 出堆后`);
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maxHeap.print();
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/* 获取堆大小 */
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let size = maxHeap.size();
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console.log(`\n堆元素数量为 ${size}`);
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/* 判断堆是否为空 */
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let isEmpty = maxHeap.isEmpty();
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console.log(`\n堆是否为空 ${isEmpty}`);
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