Linked List Cycle

gistfile1.txt

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    bool hasCycle(ListNode *head) {
        ListNode *start = head;
        ListNode *curr = start;
        
        // printf("%x\n", start);
        if (curr == 0) return false;
        
        if (curr->next == 0) return false;
        
        if (curr->next == start) return true;
        curr = curr->next;
        
        while(curr->next) {
            if (curr->next == curr) return true;
            
            ListNode *checker = start;
            while(checker != curr) {
                // printf("%x %x\n", checker, curr->next);
                if(checker == curr->next) {
                    return true;
                }    
                checker = checker->next;
            }
            
            curr =  curr->next;
        }
        
        return false;
    }
};