p50 合并二叉树 (leetcode 617)

一：解题思路

Time:O(n),Space:O(n)

二：完整代码示例 (C++版和Java版)

C++:

class Solution {
public:
    TreeNode* mergeTrees(TreeNode* t1, TreeNode* t2) 
    {
        if (t1 == NULL && t2 == NULL) return NULL;
        if ((t1 == NULL) && (t2 != NULL)) return t2;
        if ((t1 != NULL) && (t2 == NULL)) return t1;
        
        t1->val = (t1->val+t2->val);
        t1->left = mergeTrees(t1->left,t2->left);
        t1->right = mergeTrees(t1->right,t2->right);

        return t1;
    }
};

Java:

class Solution {
    public TreeNode mergeTrees(TreeNode t1, TreeNode t2)
    {
          if((t1==null)&&(t2==null)) return null;
          if((t1==null)&&(t2!=null)) return t2;
          if((t1!=null)&&(t2==null)) return t1;
          
          t1.val=t1.val+t2.val;
          t1.left=mergeTrees(t1.left,t2.left);
          t1.right=mergeTrees(t1.right,t2.right);
          
          return t1;
    }
}