【LeetCode】 Same Tree (2 solutions)

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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.

解法一：递归

/** * Definition for binary tree * 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;        else if(!p && q)            return false;        else if(p && !q)            return false;        else        {            if(p->val != q->val)                return false;            else                return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);        }    }};

解法二：非递归

建立两个队列分别进行层次遍历，进队时检查对应点是否相等

/** * Definition for binary tree * 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(!isSameNode(p, q))            return false;        if(!p && !q)            return true;                queue<TreeNode*> lqueue;        queue<TreeNode*> rqueue;        lqueue.push(p);        rqueue.push(q);        while(!lqueue.empty() && !rqueue.empty())        {            TreeNode* lfront = lqueue.front();            TreeNode* rfront = rqueue.front();            lqueue.pop();            rqueue.pop();                        if(!isSameNode(lfront->left, rfront->left))                return false;            if(lfront->left && rfront->left)            {                lqueue.push(lfront->left);                rqueue.push(rfront->left);            }                        if(!isSameNode(lfront->right, rfront->right))                return false;            if(lfront->right && rfront->right)            {                lqueue.push(lfront->right);                rqueue.push(rfront->right);            }        }        return true;    }    bool isSameNode(TreeNode* p, TreeNode *q)    {        if(!p && !q)            return true;        if((p && !q) || (!p && q) || (p->val != q->val))            return false;        return true;    }};

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