100. Same Tree

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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.

主要是二叉树的bfs的运用。

/** * 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) {         queue<TreeNode*> pque,qque;         if (p&&q)         {             pque.push(p);             qque.push(q);         }         else if (!p&&!q)  return true;         else return false;         while (!pque.empty()&&!qque.empty())         {             if (pque.front()->val!=qque.front()->val)                 return false;             else             {                 TreeNode* pp=pque.front(),*qq=qque.front();                 pque.pop();                 qque.pop();                 if (pp->left&&qq->left)                 {                    pque.push(pp->left);                    qque.push(qq->left);                 }                 else if(!pp->left&&!qq->left) {}                 else return false;                 if (pp->right&&qq->right)                 {                    pque.push(pp->right);                    qque.push(qq->right);                 }                 else if(!pp->right&&!qq->right) {}                 else return false;             }         }         if (!pque.empty()||!qque.empty())            return false;         return true;    }};

中序遍历递归实现,用的是dfs。

/** * 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);        }    }};

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