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.
分析：递归。先判断根节点的val是否相同，如相同递归的判断左子树和右子树是否分别相同。代码如下：
class Solution { public: bool isSameTree(TreeNode *p, TreeNode *q) { if(p == NULL || q == NULL) return p == q; if(p->val != q->val) return false; return isSameTree(p->left, q->left) && isSameTree(p->right, q->right); } };
原文：http://www.cnblogs.com/Kai-Xing/p/4198751.html