【leetcode】Symmetric Tree

 1 /**
 2  * Definition for binary tree
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     bool isSymmetric(TreeNode *root) {
13         if(root == NULL)
14             return true;
15         return issysmem(root->left,root->right);
16     }
17     bool issysmem(TreeNode *lc,TreeNode *rc){
18         if((!lc && rc) || (lc && !rc))
19             return false;
20         if(lc == NULL && rc == NULL)
21             return true;
22         if(lc->val != rc->val)
23             return false;
24         return issysmem(lc->left,rc->right) && issysmem(lc->right,rc->left);
25     }
26 };