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【LeetCode】Same Tree (2 solutions)

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(!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            {                    queue<TreeNode*> lq;                queue<TreeNode*> rq;                lq.push(p);                rq.push(q);                while(!lq.empty() && !rq.empty())                {                    TreeNode* lfront = lq.front();                    TreeNode* rfront = rq.front();                    lq.pop();                    rq.pop();                    if(!lfront->left && !rfront->left)                        ;// null                    else if(!lfront->left && rfront->left)                        return false;                    else if(lfront->left && !rfront->left)                        return false;                    else                    {                        if(lfront->left->val != rfront->left->val)                            return false;                        else                        {                            lq.push(lfront->left);                            rq.push(rfront->left);                        }                    }                    if(!lfront->right && !rfront->right)                        ;// null                    else if(!lfront->right && rfront->right)                        return false;                    else if(lfront->right && !rfront->right)                        return false;                    else                    {                        if(lfront->right->val != rfront->right->val)                            return false;                        else                        {                            lq.push(lfront->right);                            rq.push(rfront->right);                        }                    }                    }                return true;            }        }    }};

【LeetCode】Same Tree (2 solutions)