Merge pull request #850 from t3chkid/main

Adds solution for 287. Find the Duplicate Number in Kotlin

Author: Ahmad-A0

kotlin/287-Find-The-Duplicate-Number.kt

@@ -0,0 +1,21 @@
+package kotlin
+
+class Solution {
+    fun findDuplicate(nums: IntArray): Int {
+        var slow = 0
+        var slow2 = 0
+        var fast = 0
+        // detect the cycle
+        while (true) {
+            slow = nums[slow]
+            fast = nums[nums[fast]]
+            if (slow == fast) break
+        }
+        // get the first value at the beginning of the cycle
+        while (true) {
+            slow2 = nums[slow2]
+            slow = nums[slow]
+            if (slow2 == slow) return slow
+        }
+    }
+}