[LeetCode] Same Tree

标签：c++   leetcode   

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.

解题思路：

递归做即可。两颗二叉树相同，当且仅当当前节点值相同，并且对应的左右孩子树也相同。

/**
 * 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==NULL && q==NULL){
            return true;
        }else if(p==NULL || q==NULL){   //其中有一个是空
            return false;
        }
        if(p->val!=q->val){
            return false;
        }
        return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
    }
};

另外一种非递归法，用队列来记录两棵树当前状态：

/**
 * 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==NULL && q==NULL){
            return true;
        }else if(p==NULL || q==NULL){   //其中有一个是空
            return false;
        }
        //逻辑上，两个队列的大小相同
        queue<TreeNode*> queue1({p});
        queue<TreeNode*> queue2({q});
        while(!queue1.empty()){
            TreeNode* node1 = queue1.front();
            TreeNode* node2 = queue2.front();
            queue1.pop();
            queue2.pop();
            if(node1->val!=node2->val){
                return false;
            }
            if(node1->left!=NULL && node2->left!=NULL){
                queue1.push(node1->left);
                queue2.push(node2->left);
            }else if(node1->left!=NULL || node2->left!=NULL){
                return false;
            }
            if(node1->right!=NULL && node2->right!=NULL){
                queue1.push(node1->right);
                queue2.push(node2->right);
            }else if(node1->right!=NULL || node2->right!=NULL){
                return false;
            }
        }
        return true;
    }
};

[LeetCode] Same Tree

标签：c++   leetcode   

原文地址：http://blog.csdn.net/kangrydotnet/article/details/45790101