swap kth node from start with kth node from end in linked list: done

Author: Ram swaroop

src/me/ramswaroop/linkedlists/SwapKthNode.java

@@ -0,0 +1,75 @@
+package me.ramswaroop.linkedlists;
+
+import me.ramswaroop.common.SingleLinkedList;
+import me.ramswaroop.common.SingleLinkedNode;
+
+/**
+ * Created by IntelliJ IDEA.
+ *
+ * @author: ramswaroop
+ * @date: 7/13/15
+ * @time: 12:25 PM
+ */
+public class SwapKthNode {
+
+    public static <E extends Comparable<E>> SingleLinkedNode<E> swapKthNodeFromStartWithKthNodeFromEnd(SingleLinkedNode<E> node,
+                                                                                                       int k) {
+
+
+        int i = 1;
+
+        // dummy node needed to swap the very first node
+        SingleLinkedNode<E> head = new SingleLinkedNode<>(null),
+                curr = head,
+                slow = head,
+                fast = head,
+                temp;
+
+        head.next = node;
+
+        // find kth node from start
+        while (i < k && curr.next != null) {
+            curr = curr.next;
+            fast = fast.next;
+            i++;
+        }
+
+        // move the fast pointer k steps ahead of slow
+        fast = fast.next;
+
+        // find kth node from end
+        while (fast.next != null) {
+            slow = slow.next;
+            fast = fast.next;
+        }
+
+        // if either of the node isn't present in the list then do nothing
+        if (curr.next == null || slow.next == null) return head.next;
+
+        // swap nodes
+        temp = curr.next;
+        curr.next = slow.next;
+        slow.next = temp;
+
+        // update their next nodes
+        temp = curr.next.next;
+        curr.next.next = slow.next.next;
+        slow.next.next = temp;
+
+        return head.next;
+
+    }
+
+    public static void main(String a[]) {
+        SingleLinkedList<Integer> linkedList = new SingleLinkedList<>();
+        linkedList.add(11);
+        linkedList.add(22);
+        linkedList.add(33);
+        linkedList.add(44);
+        linkedList.add(55);
+        linkedList.add(66);
+        linkedList.add(77);
+        linkedList.printList();
+        linkedList.printList(swapKthNodeFromStartWithKthNodeFromEnd(linkedList.head, 2));
+    }
+}