hello-algo/codes/javascript/chapter_tree/binary_tree_dfs.js

/**
 * File: binary_tree.js
 * Created Time: 2022-12-04
 * Author: IsChristina (christinaxia77@foxmail.com)
 */

const { arrToTree } = require("../include/TreeNode");
const { printTree } = require("../include/PrintUtil");

// 初始化列表，用于存储遍历序列
var list = [];

/* 前序遍历 */
function preOrder(root) {
    if (root === null) return;
    // 访问优先级：根结点 -> 左子树 -> 右子树
    list.push(root.val);
    preOrder(root.left);
    preOrder(root.right);
}

/* 中序遍历 */
function inOrder(root) {
    if (root === null) return;
    // 访问优先级：左子树 -> 根结点 -> 右子树
    inOrder(root.left);
    list.push(root.val);
    inOrder(root.right);
}

/* 后序遍历 */
function postOrder(root) {
    if (root === null) return;
    // 访问优先级：左子树 -> 右子树 -> 根结点
    postOrder(root.left);
    postOrder(root.right);
    list.push(root.val);
}

/* 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
var root = arrToTree([1, 2, 3, 4, 5, 6, 7, null, null, null, null, null, null, null, null]);
console.log("\n初始化二叉树\n");
printTree(root);

/* 前序遍历 */
list.length = 0;
preOrder(root);
console.log("\n前序遍历的结点打印序列 = " + list);

/* 中序遍历 */
list.length = 0;
inOrder(root);
console.log("\n中序遍历的结点打印序列 = " + list);

/* 后序遍历 */
list.length = 0;
postOrder(root);
console.log("\n后序遍历的结点打印序列 = " + list);