C++ 代码

/**
 * 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* t1, TreeNode* t2) {
        if(!t1&&!t2){
            return nullptr;
        }
        if(!t1) return t2;
        if(!t2) return t1;
        TreeNode* root=new TreeNode(t1->val+t2->val);
        root->left=mergeTrees( t1->left, t2->left);
        root->right=mergeTrees( t1->right, t2->right);
        return root;
    }
};