Data Structure Binary Tree: Convert a given tree to its Sum Tree

http://www.geeksforgeeks.org/convert-a-given-tree-to-sum-tree/

 #include <iostream>
 #include <vector>
 #include <algorithm>
 #include <queue>
 #include <stack>
 #include <string>
 #include <fstream>
 using namespace std;

 struct node {
     int data;
     struct node *left, *right;
     node() : data(), left(NULL), right(NULL) { }
     node(int d) : data(d), left(NULL), right(NULL) { }
 };

 void prints(node *root) {
     if (!root) return;
     prints(root->left);
     cout << root->data << " ";
     prints(root->right);
 }

 int tosum(node *root) {
     if (!root) return ;
     int old = root->data;
     root->data = tosum(root->left) + tosum(root->right);
     return root->data + old;
 }

 int main() {
     node *root = new node();
     root->left = new node(-);
     root->right = new node();
     root->left->left = new node();
     root->left->right = new node(-);
     root->right->left = new node();
     root->right->right = new node();
     tosum(root);
     prints(root);
     return ;
 }