leetcode - Invert Binary Tree

leetcode - Invert Binary Tree

 

nvert a binary tree.

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

to

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

/**
 * 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(NULL == root) return root;
        //if(NULL == root->right && NULL == root->left) return root;   这句是没有必要的
        TreeNode* temp = root->right;
        root->right = invertTree(root->left);
        root->left = invertTree(temp);
    }
};

显然，使用递归。交换的时候记得先保存右树，然后将翻转后的左树赋给右指针，再将保存的右树翻转后赋给左指针。

 

附上小插曲：