Depth-first Search -- Leetcode problem100. Same Tree

描述：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：判断两棵树是否相等，水题。

思路一：递归遍历。(3ms)

class Solution {
public:
bool isSameTree(TreeNode* p, TreeNode* q) {
if (p == NULL || q == NULL) return (p == q);
if (p -> val == q -> val) {
return isSameTree(p -> left, q -> left) && isSameTree(p -> right, q -> right);
}
return false;
}
};

思路二：one line solution (0ms)

class Solution {
public:
bool isSameTree(TreeNode* p, TreeNode* q) {
return (p == NULL && q == NULL) || ((q == NULL || p == NULL) && q != NULL && p != NULL) || ((p != NULL && q != NULL) && (p -> val == q -> val) && isSameTree(p->left, q->left) && isSameTree(p->right, q->right));
}
};