Remove Kth Last Node

Author: RYMNDK

Java/src/CodeRunner/LinkedListsRunner.java

@@ -16,7 +16,9 @@ public static void main(String[] args) {
 
         // System.out.println(testLinkedListReversalRecursive());
 
-        System.out.println(testPalindromicLinkedList());
+        // System.out.println(testPalindromicLinkedList());
+
+        System.out.println(testRemoveKthLastNode());
 
         // System.out.println(testLRUCache());
 
@@ -156,6 +158,25 @@ private static boolean testPalindromicLinkedList() {
         return true;
     }
 
+    private static boolean testRemoveKthLastNode() {
+        int[] valsA = {1, 2, 3, 4, 5};
+        int k = 2;
+        ListNode headA = makeList(valsA);
+        System.out.println("Printing list A before");
+        System.out.println(listNodeToString(headA));
+
+        headA = RemoveKthLastNode.Solution(headA, k);
+
+        if (!verifyLinkedList(headA, new int[] {1, 2, 4, 5})) {
+            return false;
+        }
+
+        System.out.println("Printing list A after");
+        System.out.println(listNodeToString(headA));
+
+        return true;
+    }
+
     private static boolean testLRUCache() {
         LRUCache lru1 = new LRUCache(3);
 

Java/src/LinkedLists/RemoveKthLastNode.java

@@ -0,0 +1,46 @@
+package LinkedLists;
+
+import DS.ListNode;
+
+/*
+    // Definition of ListNode:
+    public class ListNode {
+        public int val;
+        public ListNode next;
+        public ListNode(int val) { this.val = val; }
+        public ListNode(int val, ListNode next) {
+            this(val);
+            this.next = next;
+        }
+    }
+ */
+
+
+public class RemoveKthLastNode {
+    public static ListNode Solution(ListNode head, int k) {
+        // A dummy node to ensure there's a node before 'head' in case we
+        // need to remove the head node.
+        ListNode dummy = new ListNode(-1);
+        dummy.next = head;
+        ListNode trailer = dummy;
+        ListNode leader = head;
+        // Advance 'leader' k steps ahead.
+        for (int i = 0; i < k; i++) {
+            leader = leader.next;
+            // If k is larger than the length of the linked list, no node
+            // needs to be removed.
+            if (leader == null) {
+                return head;
+            }
+        }
+        // Move 'leader' to the end of the linked list, keeping 'trailer'
+        // k nodes behind.
+        while (leader.next != null) {
+            leader = leader.next;
+            trailer = trailer.next;
+        }
+        // Remove the kth node from the end.
+        trailer.next = trailer.next.next;
+        return dummy.next;
+    }
+}