226. Invert Binary Tree（C++）

226. Invert Binary Tree

Invert a binary tree.

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

to

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

代码实现

 /**
  * 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;
         if(root->left!=nullptr||root->right!=nullptr)
         {
             swap(root->left,root->right);
             root->left=invertTree(root->left);
             root->right=invertTree(root->right);
         }
         return root;
     }
 };