617.cpp

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sample 32 ms submission
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */

static int x=[](){
std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    return 0;
}();

class Solution {
public:
    TreeNode* mergeTrees(TreeNode* t1, TreeNode* t2) {
	if (t1 == NULL)
	{
		t1 = t2;
	}
	else if (t1 != NULL && t2 != NULL)
	{
		t1->val = t1->val + t2->val;
		t1->left = mergeTrees(t1->left, t2->left);
		t1->right = mergeTrees(t1->right, t2->right);
	}
	return t1;
    }
};
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sample 13500 kb submission
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
auto __=[]()
{
    std::ios::sync_with_stdio(false);
    cin.tie(nullptr);
    return nullptr;
}();
class Solution {
public:
    TreeNode* mergeTrees(TreeNode* t1, TreeNode* t2) {
        if(!t1)
        {
            return t2;
        }
        if(!t2)
        {
            return t1;
        }
        t1->val=t1->val+t2->val;
        t1->left=mergeTrees(t1->left,t2->left);
        t1->right=mergeTrees(t1->right,t2->right);
        return t1;    
    }
};
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