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

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

 1 #include <iostream>
 2 #include <vector>
 3 #include <algorithm>
 4 #include <queue>
 5 #include <stack>
 6 #include <string>
 7 #include <fstream>
 8 using namespace std;
 9 
10 struct node {
11     int data;
12     struct node *left, *right;
13     node() : data(0), left(NULL), right(NULL) { }
14     node(int d) : data(d), left(NULL), right(NULL) { }
15 };
16 
17 void prints(node *root) {
18     if (!root) return;
19     prints(root->left);
20     cout << root->data << " ";
21     prints(root->right);
22 }
23 
24 int tosum(node *root) {
25     if (!root) return 0;
26     int old = root->data;
27     root->data = tosum(root->left) + tosum(root->right);
28     return root->data + old;
29 }
30 
31 int main() {
32     node *root = new node(10);
33     root->left = new node(-2);
34     root->right = new node(6);
35     root->left->left = new node(8);
36     root->left->right = new node(-4);
37     root->right->left = new node(7);
38     root->right->right = new node(5);
39     tosum(root);
40     prints(root);
41     return 0;
42 }