[LeetCode]Same Tree

题目描述:(链接)

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.

解题思路:

迭代版

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool isSameTree(TreeNode* p, TreeNode* q) {
        stack<TreeNode *> cache;
        cache.push(p);
        cache.push(q);
        
        while (!cache.empty()) {
            p = cache.top(); cache.pop();
            q = cache.top(); cache.pop();
            if (!p && !q) continue;
            if (!p || !q) return false;
            if (p->val != q->val) return false;
            
            cache.push(p->left);
            cache.push(q->left);
            cache.push(p->right);
            cache.push(q->right);
        }
        
        return true;
    }
};

递归版：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool isSameTree(TreeNode* p, TreeNode* q) {
        if (!p && !q) return true;
        if (!p || !q) return false;
        if (p->val != q->val) return false;
        
        return isSameTree(p->left, q->left) && isSameTree(p->right, q->right); 
    }
};