You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
hello-algo/codes/javascript/chapter_tree/array_binary_tree.js

148 lines
3.3 KiB

This file contains ambiguous Unicode characters!

This file contains ambiguous Unicode characters that may be confused with others in your current locale. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to highlight these characters.

/**
* File: array_binary_tree.js
* Created Time: 2023-08-06
* Author: yuan0221 (yl1452491917@gmail.com)
*/
const { arrToTree } = require('../modules/TreeNode');
const { printTree } = require('../modules/PrintUtil');
/* 数组表示下的二叉树类 */
class ArrayBinaryTree {
#tree;
/* 构造方法 */
constructor(arr) {
this.#tree = arr;
}
/* 列表容量 */
size() {
return this.#tree.length;
}
/* 获取索引为 i 节点的值 */
val(i) {
// 若索引越界,则返回 null ,代表空位
if (i < 0 || i >= this.size()) return null;
return this.#tree[i];
}
/* 获取索引为 i 节点的左子节点的索引 */
left(i) {
return 2 * i + 1;
}
/* 获取索引为 i 节点的右子节点的索引 */
right(i) {
return 2 * i + 2;
}
/* 获取索引为 i 节点的父节点的索引 */
parent(i) {
return Math.floor((i - 1) / 2); // 向下整除
}
/* 层序遍历 */
levelOrder() {
let res = [];
// 直接遍历数组
for (let i = 0; i < this.size(); i++) {
if (this.val(i) !== null) res.push(this.val(i));
}
return res;
}
/* 深度优先遍历 */
#dfs(i, order, res) {
// 若为空位,则返回
if (this.val(i) === null) return;
// 前序遍历
if (order === 'pre') res.push(this.val(i));
this.#dfs(this.left(i), order, res);
// 中序遍历
if (order === 'in') res.push(this.val(i));
this.#dfs(this.right(i), order, res);
// 后序遍历
if (order === 'post') res.push(this.val(i));
}
/* 前序遍历 */
preOrder() {
const res = [];
this.#dfs(0, 'pre', res);
return res;
}
/* 中序遍历 */
inOrder() {
const res = [];
this.#dfs(0, 'in', res);
return res;
}
/* 后序遍历 */
postOrder() {
const res = [];
this.#dfs(0, 'post', res);
return res;
}
}
/* Driver Code */
// 初始化二叉树
// 这里借助了一个从数组直接生成二叉树的函数
const arr = Array.of(
1,
2,
3,
4,
null,
6,
7,
8,
9,
null,
null,
12,
null,
null,
15
);
const root = arrToTree(arr);
console.log('\n初始化二叉树\n');
console.log('二叉树的数组表示:');
console.log(arr);
console.log('二叉树的链表表示:');
printTree(root);
// 数组表示下的二叉树类
const abt = new ArrayBinaryTree(arr);
// 访问节点
const i = 1;
const l = abt.left(i);
const r = abt.right(i);
const p = abt.parent(i);
console.log('\n当前节点的索引为 ' + i + ' ,值为 ' + abt.val(i));
console.log(
'其左子节点的索引为 ' + l + ' ,值为 ' + (l === null ? 'null' : abt.val(l))
);
console.log(
'其右子节点的索引为 ' + r + ' ,值为 ' + (r === null ? 'null' : abt.val(r))
);
console.log(
'其父节点的索引为 ' + p + ' ,值为 ' + (p === null ? 'null' : abt.val(p))
);
// 遍历树
let res = abt.levelOrder();
console.log('\n层序遍历为' + res);
res = abt.preOrder();
console.log('前序遍历为:' + res);
res = abt.inOrder();
console.log('中序遍历为:' + res);
res = abt.postOrder();
console.log('后序遍历为:' + res);