226

226. Invert Binary Tree (Easy)

Given the root of a binary tree, invert the tree, and return its root.

 

Example 1:

Input: root = [4,2,7,1,3,6,9]
Output: [4,7,2,9,6,3,1]

Example 2:

Input: root = [2,1,3]
Output: [2,3,1]

Example 3:

Input: root = []
Output: []

 

Constraints:

• The number of nodes in the tree is in the range [0, 100].
• -100 <= Node.val <= 100

Companies:
Amazon, Google, Adobe, Facebook, LinkedIn, Apple, VMware

Related Topics:
Tree, Depth-First Search, Breadth-First Search, Binary Tree

Solution 1.

// OJ: https://leetcode.com/problems/invert-binary-tree/
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(H)
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        if (!root) return NULL;
        swap(root->left, root->right);
        invertTree(root->left);
        invertTree(root->right);
        return root;
    }
};