Time: 6 ms (90.60%), Space: 7.4 MB (98.05%) - LeetHub

Author: knockcat

0142-linked-list-cycle-ii/0142-linked-list-cycle-ii.cpp

@@ -0,0 +1,36 @@
+/**
+ * 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) {
+        if(head ==  NULL ||  head -> next == NULL)
+            return NULL;
+        ListNode *slow = head,*fast = head, *temp = head;
+       
+        while(fast != NULL && fast -> next != NULL)
+        {
+            slow = slow -> next;
+            fast = fast -> next -> next;
+            
+            if(fast == slow)        //cycle || loop
+            {
+               while(slow != temp)
+               {
+                   slow = slow -> next;
+                   temp = temp -> next;
+               }
+                return temp ;
+            }
+               
+        }
+         
+   
+        return NULL;
+    }
+};