cc150 2.6

cyclelinklist

# include <iostream>
# inclue <map>
using namespace std;
typedef struct node{
  int data;
  node *next;
}node;
node* cyclelinklist(node *head){
  if (head=NULL) return NULL;
  node *fast=head, *slow=head;
  while (fast&&fast->next){
    fast=fast->next->next;
    slow=slow->next;
    if (slow == fast) break;
  }
  if (!fast||!fast->next) return NULL;
  fast=head;
  while (slow !=fast){
    fast=fast->next;
    slow=slow->next;
  }
  return slow;
  
}
map<node*,bool> hash;
node* cyclelinklist1 (node *head){
  if (head==NULL) return NULL;
  while (head){
    if (hash[head]) return head;
    else{
      hash[head]=true;
      head=head->next;
    }
  }
  return head;
}