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Author: hajin-kim

0019-remove-nth-node-from-end-of-list/0019-remove-nth-node-from-end-of-list.kt

@@ -0,0 +1,34 @@
+/**
+ * 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 {
+    private fun remove(head: ListNode?, n: Int, i: Int): Pair<ListNode?, Int> {
+        if (head == null) {
+            return null to i
+        }
+        val (next, lastIndex) = remove(head.next, n, i + 1)
+
+        if (lastIndex - i == n) {
+            return next to lastIndex
+        }
+        head.next = next
+        return head to lastIndex
+    }
+
+    fun removeNthFromEnd(head: ListNode?, n: Int): ListNode? {
+        if (head == null) {
+            return null
+        }
+        val (next, lastIndex) = remove(head, n, 0)
+        if (lastIndex == n) {
+            return next
+        }
+        return head
+    }
+}