617. Merge Two Binary Trees.cpp

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