72_symmetrictree.cpp

//https://leetcode.com/problems/symmetric-tree/description/

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */

        class Solution {
public:
    bool isIdentical(TreeNode* r1, TreeNode* r2){
        if(!r1 && !r2) return true;
        if(!r1 || !r2) return false;
        if( r1->val != r2->val) return false;
        return (isIdentical(r1->left,r2->right) && isIdentical(r1->right,r2->left));
    }
    bool isSymmetric(TreeNode* root)
    {
        if(root == NULL) return true;
	    return isIdentical(root,root);
    }
};