[SeongA] WEEK 09 solutions

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
+    }
+}
+

sum-of-two-integers/delight010.swift

@@ -0,0 +1,18 @@
+class Solution {
+    // Time O(log n)
+    // Space O(1)
+    func getSum(_ a: Int, _ b: Int) -> Int {
+        var a = a
+        var b = b
+
+        while b != 0 {
+            var sum = a ^ b
+            var carry = (a & b) << 1
+            a = sum
+            b = carry
+        }
+
+        return a
+    }
+}
+