[LeetCode]Linked List Cycle II

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode *detectCycle(ListNode *head) {
// IMPORTANT: Please reset any member data you declared, as
// the same Solution instance will be reused for each test case.
ListNode* fastWalker = head;
if(hasCycle(head, fastWalker))
{
ListNode* cur = head;
while(cur != fastWalker)
{
cur = cur->next;
fastWalker = fastWalker->next;
}
return cur;
}
else return NULL;
}
private:
bool hasCycle(ListNode *head, ListNode*& fastWalker) {
// IMPORTANT: Please reset any member data you declared, as
// the same Solution instance will be reused for each test case.
ListNode* slowWalker = head;

while(fastWalker && slowWalker)
{
fastWalker = fastWalker->next;
if(fastWalker) fastWalker = fastWalker->next;
else break;
slowWalker = slowWalker->next;

if(fastWalker == slowWalker) return true;
}

return false;
}
};