Create 0024-swap-nodes-in-pairs.kt

Author: a93a

Diff for: kotlin/0024-swap-nodes-in-pairs.kt

@@ -0,0 +1,30 @@
+/**
+ * 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 swapPairs(head: ListNode?): ListNode? {
+        var dummy = ListNode(0, head)
+        var prev = dummy
+        var cur = head
+
+        while (cur != null && cur.next != null) {
+            val next = cur.next
+            val nextNext = cur.next.next
+
+            next.next = cur
+            cur.next = nextNext
+            prev.next = next
+
+            prev = cur
+            cur = nextNext
+        }
+
+        return dummy.next
+    }
+}