DaleStudy#225 Linked List Cycle

Author: forest000014

linked-list-cycle/forest000014.java

@@ -0,0 +1,29 @@
+/**
+ # Time Complexity : O(n)
+ # Space Complexity: O(1)
+
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode(int x) {
+ *         val = x;
+ *         next = null;
+ *     }
+ * }
+ */
+public class Solution {
+    private final int VISITED = -999999;
+    public boolean hasCycle(ListNode head) {
+        while (head != null) {
+            if (head.val == VISITED) {
+                return true;
+            }
+
+            head.val = VISITED;
+            head = head.next;
+        }
+
+        return false;
+    }
+}