226. Invert Binary Tree

Invert a binary tree.

     4   /   \  2     7 / \   / \1   3 6   9

to

     4   /   \  7     2 / \   / \9   6 3   1

递归遍历交换节点即可

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    TreeNode* invertTree(TreeNode* root) {        if(!root) return root;        TreeNode* temp;        temp = root->left;        root->left = root->right;        root->right = temp;        invertTree(root->left);        invertTree(root->right);        return root;    }};