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94.二叉树的中序遍历 (opens new window)

Tags: algorithms microsoft hash-table stack tree

Langs: c cpp csharp golang java javascript kotlin php python python3 ruby rust scala swift typescript

• algorithms
• Medium (73.85%)
• Likes: 755
• Dislikes: -
• Total Accepted: 288.2K
• Total Submissions: 389.8K
• Testcase Example: '[1,null,2,3]'

给定一个二叉树，返回它的中序 遍历。

示例:

输入: [1,null,2,3]
   1
    \
     2
    /
   3

输出: [1,3,2]

进阶: 递归算法很简单，你可以通过迭代算法完成吗？

/*
 * @lc app=leetcode.cn id=94 lang=javascript
 *
 * [94] 二叉树的中序遍历
 */

// @lc code=start
/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number[]}
 */
//递归
var inorderTraversal = function (root) {
    if (root === null) return []
    return [...inorderTraversal(root.left), root.val, ...inorderTraversal(root.right)]
};
var inorderTraversal = function (root) {
    let ret = [],
        stack = [], p = root;
    while (p || stack.length) {
        if (p) {
            stack.push(p);
            p = p.left;
        } else {
            p = stack.pop();
            ret.push(p.val);
            p = p.right;
        }
    }
    return ret;
};
// @lc code=end