No.94 二叉树的中序遍历
给定一个二叉树的根节点 root ,返回 它的 中序 遍历 。
示例 1:
text
输入:root = [1,null,2,3]
输出:[1,3,2]
示例 2:
text
输入:root = []
输出:[]
示例 3:
text
输入:root = [1]
输出:[1]
提示:
- 树中节点数目在范围 [0, 100] 内
- -100 <= Node.val <= 100
进阶: 递归算法很简单,你可以通过迭代算法完成吗?
解题思路
实现
深度优先搜索 - dfs
js
/**
* 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;
}
/**
* dfs
* @param {TreeNode} root
* @return {number[]}
*/
var inorderTraversal = function (root) {
let res = [];
const dfs = (node) => {
if (!node) return;
dfs(node.left);
res.push(node.val);
dfs(node.right);
};
dfs(root);
return res;
};
广度优先搜索 - bfs
js
/**
* 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[]}
*/
var inorderTraversal = function (root) {
let stack = [];
let res = [];
while (stack.length || root) {
while (root) {
stack.push(root);
root = root.left;
}
root = stack.pop();
res.push(root.val);
root = root.right;
}
return res;
};