Add reverse linked list solution

Author: hyunjung-choi

reverse-linked-list/hyunjung-choi.kt

@@ -0,0 +1,25 @@
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+
+class Solution {
+    fun reverseList(head: ListNode?): ListNode? {
+        var prev: ListNode? = null
+        var current = head
+
+        while (current != null) {
+            val next = current.next
+            current.next = prev
+            prev = current
+            current = next
+        }
+
+        return prev
+    }
+}