LeetCode: Symmetric Tree

思路：镜像树中，对于同一层处于镜像位置的两个节点A,B，A的左孩子需要与B的右孩子相同，A的右孩子需要与B的左孩子相同，依次递归这个过程即可

code:

class Solution {public:    bool isSym(TreeNode * left,TreeNode * right){        if(left != NULL && right != NULL)            return left->val == right->val && isSym(left->left,right->right) && isSym(left->right,right->left);        if(left == NULL && right == NULL)            return true;        return false;            }    bool isSymmetric(TreeNode *root) {        if(root == NULL)return true;        return isSym(root->left,root->right);    }};