Find duplicate elements in an array

src/main/kotlin/Main.kt

@@ -30,4 +30,11 @@ fun main() {
     node3.next = node1 // cycle back to x
     val llcdResult = linkedListCycleDetection.hasCycle(node1)
     println("Has cycle $llcdResult")
+
+    // Calling Contains Duplicate
+    val `containsDuplicate.kt` = `ContainsDuplicate.kt`()
+    val containsDuplicateResult = `containsDuplicate.kt`
+        .containsDuplicate(intArrayOf(1,2,3,1,0,1))
+    println("Contains Duplicate Integers $containsDuplicateResult")
+
 }

src/main/kotlin/dsalgoleetcode/ContainsDuplicate.kt.kt

@@ -0,0 +1,27 @@
+package main.kotlin.dsalgoleetcode
+
+/**
+ * Contains Duplicate
+ * Given an integer array nums, return true if any value appears at least twice in the
+ * array, and return false if every element is distinct.
+ *
+ * Example 1:
+ * Input: nums = [1,2,3,1]
+ * Output: true
+ * Explanation:
+ * The element 1 occurs at the indices 0 and 3.
+ * */
+
+class `ContainsDuplicate.kt` {
+
+    fun containsDuplicate(nums: IntArray): Boolean {
+
+        val seen = mutableSetOf<Int>()
+        for(i in nums){
+            if( i in seen)
+                return true
+            seen.add(i)
+        }
+        return false
+    }
+}