leetcode——226—— Invert Binary Tree

Invert Binary Tree

  Total Accepted: 11286   Total Submissions: 32033

Invert a binary tree.

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

to

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

Trivia:
This problem was inspired by  this original tweet  by  Max Howell :

Google: 90% of our engineers use the software you wrote (Homebrew), but you can’t invert a binary tree on a whiteboard so fuck off.

[思路]

递归交换左右子树

[CODE]

/**
 * 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==NULL)
          return root;
          
        TreeNode*  pTemp = root->left;
        root->left = root->right;
        root->right = pTemp;
        
        if(root->left)
           invertTree(root->left);
         
        if(root->right)
           invertTree(root->right);
           
        return root;
    } 
};