617. Merge Two Binary Trees

https://www.cnblogs.com/grandyang/p/7058935.html

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