Data Structure Binary Tree: Diameter of a Binary Tree

http://www.geeksforgeeks.org/diameter-of-a-binary-tree/
 1 #include <iostream>
 2 #include <vector>
 3 #include <algorithm>
 4 #include <queue>
 5 #include <stack>
 6 using namespace std;
 7 
 8 struct node {
 9     int data;
10     struct node *left, *right;
11     node() : data(0), left(NULL), right(NULL) { }
12     node(int d) : data(d), left(NULL), right(NULL) { }
13 };
14 
15 void print(node *node) {
16     if (!node) return;
17     print(node->left);
18     cout << node->data << " ";
19     print(node->right);
20 }
21 
22 int diameter(node *root, int &ans) {
23     if (!root) return 0;
24     int l = diameter(root->left, ans);
25     int r = diameter(root->right, ans);
26     ans = max(ans, l+r+1);
27     return max(l, r) + 1;
28 }
29 
30 
31 int main() {
32     struct node* root = new node(1);
33     root->left = new node(2);
34     root->right = new node(3);
35     root->left->left = new node(4);
36     root->left->right = new node(5);
37     int ans = 0;
38     diameter(root, ans);
39     cout << ans << endl;
40     return 0;
41 }