Create 0876-middle-of-the-linked-list.kt

Author: a93a

kotlin/0876-middle-of-the-linked-list.kt

@@ -0,0 +1,21 @@
+/**
+ * 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 {
+    // use two pointers, fast one that is 2x fast as slow, which will reach end when slow reaches mid
+    fun middleNode(head: ListNode?): ListNode? {
+        if(head == null) return null
+        var slow = head; var fast = head
+        while(fast != null && fast?.next != null){
+            slow = slow?.next
+            fast = fast?.next?.next
+        }
+        return slow
+    }
+}