Data Structure Binary Tree: Diameter of a Binary Tree

http://www.geeksforgeeks.org/diameter-of-a-binary-tree/

 #include <iostream>
 #include <vector>
 #include <algorithm>
 #include <queue>
 #include <stack>
 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 print(node *node) {
     if (!node) return;
     print(node->left);
     cout << node->data << " ";
     print(node->right);
 }

 int diameter(node *root, int &ans) {
     if (!root) return ;
     int l = diameter(root->left, ans);
     int r = diameter(root->right, ans);
     ans = max(ans, l+r+);
     return max(l, r) + ;
 }

 int main() {
     struct node* root = new node();
     root->left = new node();
     root->right = new node();
     root->left->left = new node();
     root->left->right = new node();
     int ans = ;
     diameter(root, ans);
     cout << ans << endl;
     return ;
 }