Data Structure Linked List: Detect and Remove Loop in a Linked List

http://www.geeksforgeeks.org/detect-and-remove-loop-in-a-linked-list/

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

struct node {
    int data;
    node *next;
    node() : data(0), next(NULL) { }
    node(int d) : data(d), next(NULL) { }
};

void push(node* &head, int k) {
    node *new_node = new node(k);
    new_node->next = head;
    head = new_node;
}

void detectandremove(node *&head) {
    node *p, *q;
    p = q = head;
    while (q && q->next) {
        q = q->next->next;
        p = p->next;
        if (p == q) break;
    }
    if (!q || !q->next) return; //no loop
    q = head;
    while (q != p) {
        q = q->next;
        p = p->next;
    } //get the starting point of the ring
    while (q->next != p) q = q->next; //get the point before the starting point of the ring
    q->next = NULL; //remove the ring
}

void print(node *head) {
    while (head) {
        cout << head->data << " ";
        head = head->next;
    }
}

int main() {
    node *head = NULL;
    push(head, 10);
    push(head, 4);
    push(head, 15);
    push(head, 20);
    push(head, 50);
    push(head, 60);
    head->next->next->next->next->next->next = head->next->next->next;
    detectandremove(head);
    print(head);
    return 0;
}