rotate-right.c

#include <stdio.h>


struct ListNode
{
	int val;
	struct ListNode *next;
};

int getSize(struct ListNode *head)
{
	int size = 0;
	while (head) {
		size++;
		head = head->next;
	}
	return size;
}

struct ListNode *rotateRight(struct ListNode *head, int k)
{
	int size = getSize(head);
	if (size == 0) {
		return head;
	}

	struct ListNode *current = head;
	struct ListNode *split, *end;

	k = k % size;
	k = size - k;
	if (k == 0) {
		return head;
	}

	int i = 1;
	while (current) {
		if (i == k) {
			split = current;
		}
		end = current;
		current = current->next;
		++i;
	}
	end->next = head;
	head = split->next;
	split->next = NULL;
	return head;
}

int main()
{
	struct ListNode n7 = {7, NULL};
	struct ListNode n6 = {6, &n7};
	struct ListNode n5 = {5, NULL};
	struct ListNode n4 = {4, &n5};
	struct ListNode n3 = {3, &n4};
	struct ListNode n2 = {2, &n3};
	struct ListNode n1 = {1, &n2};

	struct ListNode *result = rotateRight(&n1, 2);
	printf("\nSize: %d\n", getSize(result));
	while (result != NULL) {
		printf("%d ", result->val);
		result = result->next;
	}

}