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.

 

分析：注意边界条件的判断，先判断两树是不是为空，都为空，则为true，否则递归判断存在的其他情况，判断左右子树的情况。

/**

 * 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==NULL&&q==NULL)

            return true;

        else if(p&&q)

        {

            if(p->val==q->val)

            {

                return isSameTree(p->left,q->left)&&isSameTree(p->right,q->right);

            }

            else

            {

                return false;

            }

        }

        else

        {

            return false;

        }

    }

};

 python：

# Definition for a  binary tree node

# class TreeNode:

#     def __init__(self, x):

#         self.val = x

#         self.left = None

#         self.right = None



class Solution:

    # @param p, a tree node

    # @param q, a tree node

    # @return a boolean

    def isSameTree(self, p, q):

        if p==None and q==None:

            return True

        elif p!=None and q==None:

            return False

        elif p==None and q!=None:

            return False

        elif p!=None and q!=None and p.val!=q.val:

            return False

        else:

            return self.isSameTree(p.left,q.left) and self.isSameTree(p.right,q.right)