【LeetCode】226

Invert a binary tree.

     4
   /   
  2     7
 /    / 
1   3 6   9

         to

     4
   /   
  7     2
 /    / 
9   6 3   1

 

Notice: 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.

 

Solution: recursion

/**
 * 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 NULL;
        else{
            TreeNode *newleft=invertTree(root->right);
            TreeNode *newright=invertTree(root->left);
            root->left=newleft;
            root->right=newright;
            return root;
        }
    }
};