solves rotate list

Author: anishLearnsToCode

README.md

@@ -58,6 +58,7 @@
 |  57  | [Insert Interval](https://leetcode.com/problems/insert-interval)                                                                                          |                                                                 [![Java](assets/java.png)](src/InsertInterval.java)                                                                  |                                                                                                                                   |
 |  58  | [Length of Last Word](https://leetcode.com/problems/length-of-last-word)                                                                                  |                                 [![Java](assets/java.png)](src/LengthOfLastWord.java) [![Python](assets/python.png)](python/length_of_last_word.py)                                  |                                                                                                                                   |
 |  59  | [Spiral Matrix II](https://leetcode.com/problems/spiral-matrix-ii)                                                                                        |                                                                 [![Java](assets/java.png)](src/SpiralMatrixII.java)                                                                  |                                                                                                                                   |
+|  61  | [Rotate List](https://leetcode.com/problems/rotate-list)                                                                                                  |                                                                   [![Java](assets/java.png)](src/RotateList.java)                                                                    |                                                                                                                                   |
 |  66  | [Plus One](https://leetcode.com/problems/plus-one)                                                                                                        |                                           [![Java](assets/java.png)](src/PlusOne.java) [![Python](assets/python.png)](python/plus_one.py)                                            |                                                                                                                                   |
 |  67  | [Add Binary](https://leetcode.com/problems/add-binary)                                                                                                    |                                         [![Java](assets/java.png)](src/AddBinary.java) [![Python](assets/python.png)](python/add_binary.py)                                          |                                                                                                                                   |
 |  69  | [Sqrt(x)](https://leetcode.com/problems/sqrtx)                                                                                                            |                                              [![Java](assets/java.png)](src/Sqrtx.java) [![Python](assets/python.png)](python/sqrt.py)                                               |                                                                                                                                   |

src/RotateList.java

@@ -0,0 +1,52 @@
+// https://leetcode.com/problems/rotate-list
+// T: O(N)
+// S: O(1)
+
+public class RotateList {
+    public static class ListNode {
+        int val;
+        ListNode next;
+        ListNode() {}
+        ListNode(int val) { this.val = val; }
+        ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+    }
+
+    public ListNode rotateRight(ListNode head, int k) {
+        final int length = getLength(head);
+        if (length == 0) return head;
+        final int rotations = k % length;
+        if (rotations == 0) return head;
+        final ListNode last = getLastNode(head);
+        final ListNode cutoffNode = getCutoffNode(head, rotations, length);
+        final ListNode newHead = cutoffNode.next;
+        last.next = head;
+        cutoffNode.next = null;
+        return newHead;
+    }
+
+    private int getLength(ListNode head) {
+        int length = 0;
+        ListNode current = head;
+        while (current != null) {
+            current = current.next;
+            length++;
+        }
+        return length;
+    }
+
+    private ListNode getLastNode(ListNode head) {
+        ListNode current = head;
+        while (current.next != null) {
+            current = current.next;
+        }
+        return current;
+    }
+
+    private ListNode getCutoffNode(ListNode head, int rotations, int length) {
+        ListNode current = head;
+        for (int i = 0 ; i < length - rotations - 1 ; i++) {
+            current = current.next;
+        }
+        return current;
+    }
+}