61. | Rotate List | C

Author: subratkatiyar

C/Rotate_List.c

@@ -0,0 +1,47 @@
+/*
+https://leetcode.com/problems/rotate-list/submissions/
+*/
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     struct ListNode *next;
+ * };
+ */
+
+
+struct ListNode *rotateRight(struct ListNode *head, int k) {
+    if (!head || k == 0) return head;
+
+/*
+Used to count the size of the array.
+*/
+	struct ListNode* lastNode = head;
+	int n = 1;
+	while (lastNode->next)
+	{
+		lastNode = lastNode->next;
+		n++;
+	}
+
+/*
+Used to remove any complete rotations from the list.
+Example: If size of list is n, and no. of rotations = k
+if (n==k)
+then no rotations is required.
+so n = n%k removes all complete roations.
+*/
+	k = k%n;
+	if (k == 0) return head;
+	k = n - k;
+
+	lastNode->next = head;
+	struct ListNode *newHead = head;
+
+	for (int i = 0; i < k - 1; i++)
+		newHead = newHead->next;
+
+	head = newHead->next;
+	newHead->next = NULL;
+	return head;
+}