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141.LinkedListCycle.cpp
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141.LinkedListCycle.cpp
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#include<bits/stdc++.h>
using namespace std;
struct ListNode {
int val;
ListNode *next;
ListNode(int x) : val(x), next(NULL) {}
};
class Solution {
public:
struct ListNode {
int val;
ListNode *next;
ListNode(int x) : val(x), next(NULL) {}
};
bool hasCycle(ListNode *head) {
ListNode *slow=head; // taking the slow pointer to travel the single distance
ListNode *fast=head; // taking the fast pointer to travel the double distance
while(fast!=NULL && fast->next!=NULL) // while travelling, if they are not cyclic fast or fast's next will reach the end [NULL]
{
slow=slow->next; // slow travels 1 step
fast=fast->next->next; // fast travels 2 step
if(slow==fast) // when they match
{
return slow; // return slow if the
}
}
return NULL;
}
// return NULL if they dont meet proving acyclic linked list
};