[LeetCode]226. Invert Binary Tree(反转二叉树)

226. Invert Binary Tree

Invert a binary tree.反转二叉树

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

to

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

用递归，交换各个节点的左右节点
代码如下：

C++

/**
 * 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;
        TreeNode* temp = root->left;
        root->left = root->right;
        root->right = temp;

        invertTree(root->left);
        invertTree(root->right);

        return root;
    }
};

当然，非递归更好，查阅了一些非递归方法，讲解很详细
链接1 http://www.2cto.com/kf/201506/410311.html
链接2 http://blog.youkuaiyun.com/booirror/article/details/46496719