Given two binary trees and imagine that when you put one of them to cover the other, some nodes of the two trees are overlapped while the others are not.

You need to merge them into a new binary tree. The merge rule is that if two nodes overlap, then sum node values up as the new value of the merged node. Otherwise, the NOT null node will be used as the node of new tree.

Example 1:

Input:

    Tree 1                     Tree 2                  
          1                         2                             
         / \                       / \                            
        3   2                     1   3                        
       /                           \   \                      
      5                             4   7                  

Output:

Merged tree:
         3
        / \
       4   5
      / \   \ 
     5   4   7

Note:The merging process must start from the root nodes of both trees.

/**

* 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:

TreeNode\* mergeTrees\(TreeNode\* t1, TreeNode\* t2\) {

    TreeNode \*result;

    result=\(TreeNode \*\)malloc\(sizeof\(TreeNode\)\);

    result->left=NULL; result->right=NULL;

    if \(\(t1!=NULL\)&&\(t2!=NULL\)\){

        result->val=t1->val+t2->val;

        result->left=mergeTrees\(t1->left, t2->left\);

        result->right=mergeTrees\(t1->right, t2->right\);

    }

    else if \(\(t1!=NULL\)&&\(t2==NULL\)\){

        result->val=t1->val;

        result->left=t1->left;

        result->right=t1->right;

    }

    else if \(\(t1==NULL\)&&\(t2!=NULL\)\){

        result->val=t2->val;

         result->left=t2->left;

        result->right=t2->right;

    }

    else{

       result=NULL;

    }

    return result;

}

};

记住怎么申请空间然后一定要让左边和右边都是空的，反正就是保证每个地方都又明确的指令是什么