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.
判断两棵树是否相同：1）如果两棵树的对应节点都为空，返回true。2）如果只有1课树的节点为空，返回false。3）如果两棵树的当前节点值相同，则递归判断下一个对应的节点。4）如果都不满足以上，则返回false。
class Solution { public: bool isSameTree(TreeNode* p, TreeNode* q) { if (p == nullptr && q == nullptr) return true; if (p == nullptr || q == nullptr) return false; if (p->val == q->val) return isSameTree(p->left, q->left) && isSameTree(p->right, q->right); return false; } }; // 0 ms
以上过程的简洁写法。
class Solution { public: bool isSameTree(TreeNode* p, TreeNode* q) { if (p == nullptr || q == nullptr) return p == q; return (p->val == q->val) && isSameTree(p->left, q->left) && isSameTree(p->right, q->right); } }; // 3 ms
原文：http://www.cnblogs.com/immjc/p/7192016.html