此篇文章為我的解題紀錄，程式碼或許並不是很完善

Leetcode - 617. Merge Two Binary Trees

解題思路

使用recusive來將每個子節點相加到第一個樹，若是第一個樹在該位置無節點則創建新的點

我滴程式碼

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* mergeTrees(TreeNode* root1, TreeNode* root2) {
        if (root1 == NULL && root2 == NULL)
        {
            return NULL;
        }
        else if (root1 == NULL)
        {
            return root2;
        }
        else if (root2 == NULL)
        {
            return root1;
        }
        else
        {
            root1->val += root2->val;
            root1->left = mergeTrees(root1->left, root2->left);
            root1->right = mergeTrees(root1->right, root2->right);
        }
        return root1;
    }
};