Rotate Linked List

Author: saurabhchris1

Rotate_Linked_List.py

@@ -0,0 +1,54 @@
+# Given a linked list, rotate the list to the right by k places, where k is non-negative.
+#
+# Example 1:
+#
+# Input: 1->2->3->4->5->NULL, k = 2
+# Output: 4->5->1->2->3->NULL
+# Explanation:
+# rotate 1 steps to the right: 5->1->2->3->4->NULL
+# rotate 2 steps to the right: 4->5->1->2->3->NULL
+# Example 2:
+#
+# Input: 0->1->2->NULL, k = 4
+# Output: 2->0->1->NULL
+# Explanation:
+# rotate 1 steps to the right: 2->0->1->NULL
+# rotate 2 steps to the right: 1->2->0->NULL
+# rotate 3 steps to the right: 0->1->2->NULL
+# rotate 4 steps to the right: 2->0->1->NULL
+
+
+class ListNode:
+    def __init__(self, x):
+        self.val = x
+        self.next = None
+
+
+class Solution:
+    def rotateRight(self, head, k):
+        if not head:
+            return head
+        if not head.next:
+            return head
+
+        length = 0
+        curr = head
+        while curr:
+            length += 1
+            curr = curr.next
+
+        k = k % length
+        slow = fast = head
+
+        for _ in range(k):
+            fast = fast.next
+
+        while fast.next:
+            slow = slow.next
+            fast = fast.next
+
+        fast.next = head
+        head = slow.next
+        slow.next = None
+
+        return head