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(0), 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 0;
    int l = diameter(root->left, ans);
    int r = diameter(root->right, ans);
    ans = max(ans, l+r+1);
    return max(l, r) + 1;
}


int main() {
    struct node* root = new node(1);
    root->left = new node(2);
    root->right = new node(3);
    root->left->left = new node(4);
    root->left->right = new node(5);
    int ans = 0;
    diameter(root, ans);
    cout << ans << endl;
    return 0;
}