[OJ.leetcode] same-tree

https://oj.leetcode.com/problems/same-tree/ 

 Given two binary trees, write a function to check if they are equal or not. 

 Two binary trees are considered equal if they are structurally identical and the nodes have the same value.

/** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ /* Goal: no bug, no fixed, go accepted at the first try base case: left == null && right ==null preorder traversal : O(n) test case: {1},{1} {}, {} {0,1}, {0,1,2} 한번에 수정없이 accepted 성공! */ class Solution { public: bool isSameTree(TreeNode *p, TreeNode *q) { if(p == NULL && q == NULL) return true; else if(!p || !q) return false; if(p->val != q->val) return false; return isSameTree(p->left, q->left) && isSameTree(p->right, q->right); } };