hello-algo/codes/javascript/chapter_heap/my_heap.js
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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

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Co-authored-by: Yudong Jin <krahets@163.com>
2023-02-07 20:48:54 +08:00

160 lines
4 KiB
JavaScript

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