Remove loop-detection logic and tests.

Author: newboadki

Singly Linked List/SinglyLinkedList.swift

@@ -198,34 +198,6 @@ public struct SinglyLinkedList<T>
         return self.find(kthToLast: kthToLast, startingAt: self.storage.head, count: UInt(self.count))
     }
 
-    
-    
-    // MARK: LOOP DETECTION
-    
-    /// A singly linked list contains a loop if one node references back to a previous node.
-    ///
-    /// - Returns: Whether the linked list contains a loop
-    public func containsLoop() -> Bool
-    {
-        /// Advances a node at a time
-        var current = self.storage.head
-        
-        /// Advances twice as fast
-        var runner = self.storage.head
-        
-        while (runner != nil) && (runner?.next != nil) {
-            
-            current = current?.next
-            runner = runner?.next?.next
-            
-            if runner === current {
-                return true
-            }
-        }
-        
-        return false
-    }
-    
 }
 
 
@@ -261,25 +233,17 @@ private extension SinglyLinkedList {
             // Copy on write: we are about to modify next a property in
             // a potentially shared node. Make sure it's new if necessary.
             self.storageForWritting.tail?.next = node
-            if !self.containsLoop() {
-                let (tail, _) = findTail(in: node)
-                self.storageForWritting.tail = tail // There
-            } else {
-                self.storageForWritting.tail = nil
-            }
+            let (tail, _) = findTail(in: node)
+            self.storageForWritting.tail = tail // There
         }
         else
         {
             // This also means that there's no head.
             // Otherwise the state would be inconsistent.
             // This will be checked when adding and deleting nodes.
             self.storageForWritting.head = node
-            if !self.containsLoop() {
-                let (tail, _) = findTail(in: node)
-                self.storageForWritting.tail = tail // There
-            } else {
-                self.storageForWritting.tail = nil
-            }
+            let (tail, _) = findTail(in: node)
+            self.storageForWritting.tail = tail // There
         }
     }
 

Singly Linked List/Tests/Tests/SinglyLinkedListTests.swift

@@ -120,48 +120,6 @@ class SinglyLinkedListTests: XCTestCase {
         XCTAssertTrue(list.find(kthToLast: 7)?.value == 2)
         XCTAssertTrue(list.find(kthToLast: 8)?.value == 2)
         XCTAssertTrue(list.find(kthToLast: 9)?.value == nil)
-        XCTAssertFalse(list.containsLoop())
-    }
-    
-    func testContainsLoop() {
-        let n1 = SinglyLinkedListNode<Int>(value: 1)
-        let n2 = SinglyLinkedListNode<Int>(value: 2)
-        let n3 = SinglyLinkedListNode<Int>(value: 3)
-        let n4 = SinglyLinkedListNode<Int>(value: 4)
-        let n5 = SinglyLinkedListNode<Int>(value: 5)
-        let n6 = SinglyLinkedListNode<Int>(value: 6)
-        let n7 = SinglyLinkedListNode<Int>(value: 7)
-        let n8 = SinglyLinkedListNode<Int>(value: 8)
-        n1.next = n2
-        n2.next = n3
-        n3.next = n4
-        n4.next = n5
-        n5.next = n6
-        n6.next = n7
-        n7.next = n8
-        n8.next = n2
-        
-        let list = SinglyLinkedList<Int>(head: n1)
-        XCTAssertTrue(list.containsLoop())
-        XCTAssertTrue(list.last == nil)
-    }
-    
-    func testContainsLoopFalseWithLiterals() {
-        let list: SinglyLinkedList<Int> = [1,2,3,4,5,6,7,8]
-        XCTAssertTrue(list.last == 8, "Found \(String(describing: list.last))")
-        XCTAssertFalse(list.containsLoop())
-    }
-    
-    func testContainsLoopFalseWithNodes() {
-        let n1 = SinglyLinkedListNode<Int>(value: 1)
-        let n2 = SinglyLinkedListNode<Int>(value: 2)
-        let n3 = SinglyLinkedListNode<Int>(value: 3)
-        n1.next = n2
-        n2.next = n3
-        
-        let list = SinglyLinkedList<Int>(head: n1)
-        XCTAssertFalse(list.containsLoop())
-        
     }
 
     func testConstructorFromArrayLiteralWhenEmpty() {
@@ -178,7 +136,6 @@ class SinglyLinkedListTests: XCTestCase {
         XCTAssertTrue(list.count == 1, "Found \(list.count)")
     }
 
-    
     func testAppendValue() {
         var list = SinglyLinkedList<Int>()
         list.append(value: 1)