solve problem

Author: delight010

linked-list-cycle/delight010.swift

@@ -0,0 +1,29 @@
+public class ListNode {
+    public var val: Int
+    public var next: ListNode?
+    public init(_ val: Int) {
+        self.val = val
+        self.next = nil
+    }
+}
+
+
+class Solution {
+    // Time O(n)
+    // Space O(1)
+    func hasCycle(_ head: ListNode?) -> Bool {
+        var slow: ListNode? = head
+        var fast: ListNode? = head
+        
+        while fast != nil && fast?.next != nil {
+            slow = slow?.next
+            fast = fast?.next?.next
+            
+            if slow === fast {
+                return true
+            }
+        }
+        return false
+    }
+}
+