ConstDefinition for a binary tree node. class TreeNode { val: number left: TreeNode | null right: TreeNode | null constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) { this.val = (val===undefined ? 0 : val) this.left = (left===undefined ? null : left) this.right = (right===undefined ? null : right) } }
翻转二叉树，就是将二叉树的左右子树交换。
/**
* Definition for a binary tree node.
* class TreeNode {
* val: number
* left: TreeNode | null
* right: TreeNode | null
* constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
* this.val = (val===undefined ? 0 : val)
* this.left = (left===undefined ? null : left)
* this.right = (right===undefined ? null : right)
* }
* }
*/
function invertTree(root: TreeNode | null): TreeNode | null {
function dfs(node: TreeNode | null) {
if (!node) {
return null;
}
const left = dfs(node.left);
const right = dfs(node.right);
node.left = right;
node.right = left;
return node;
}
return dfs(root);
};
226.翻转二叉树
给你一棵二叉树的根节点
root，翻转这棵二叉树，并返回其根节点。示例 1：
输入：
root = [4,2,7,1,3,6,9]输出：
[4,7,2,9,6,3,1]示例 2：
root = [2,1,3]输出：
[2,3,1]示例 3：
输入：
root = []输出：
[]提示：
[0, 100]内-100 <= Node.val <= 100