diff --git a/codes/javascript/chapter_heap/my_heap.js b/codes/javascript/chapter_heap/my_heap.js new file mode 100644 index 000000000..945b7a178 --- /dev/null +++ b/codes/javascript/chapter_heap/my_heap.js @@ -0,0 +1,160 @@ +/** + * 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} 后`); + 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}`); diff --git a/codes/javascript/include/PrintUtil.js b/codes/javascript/include/PrintUtil.js index a9d500af7..8d7a25d5e 100644 --- a/codes/javascript/include/PrintUtil.js +++ b/codes/javascript/include/PrintUtil.js @@ -4,6 +4,8 @@ * Author: IsChristina (christinaxia77@foxmail.com) */ +const { arrToTree } = require("./TreeNode"); + /** * Print a linked list * @param head @@ -82,7 +84,19 @@ function showTrunks(p) { process.stdout.write(p.str); } +/** + * Print a heap + * @param arr + */ +function printHeap(arr) { + console.log("堆的数组表示:"); + console.log(arr); + console.log("堆的树状表示:"); + printTree(arrToTree(arr)); +} + module.exports = { printLinkedList, - printTree -} + printTree, + printHeap, +}; diff --git a/docs/chapter_heap/heap.md b/docs/chapter_heap/heap.md index 74d632397..4fa839a1b 100644 --- a/docs/chapter_heap/heap.md +++ b/docs/chapter_heap/heap.md @@ -29,11 +29,11 @@ comments: true