ronith
7/23/2018 - 7:17 AM

Given a singly linked list, rotate the linked list counter-clockwise by k nodes. Where k is a given positive integer. For example, if the given linked list is 10->20->30->40->50->60 and k is 4, the list should be modified to 50->60->10->20->30->40. Assume that k is smaller than the count of nodes in linked list.

Algorithm: To rotate the linked list, we need to change next of kth node to NULL, next of last node to previous head node, and finally change head to (k+1)th node. So we need to get hold of three nodes: kth node, (k+1)th node and last node. Traverse the list from beginning and stop at kth node. Store pointer to kth node. We can get (k+1)th node using kthNode->next. Keep traversing till end and store pointer to last node also. Finally, change pointers as stated above.

``````// https://www.geeksforgeeks.org/rotate-a-linked-list/
#include <iostream>
#include <list>
using namespace std;

int data;
};

void print (node *n) {
while (n) {
cout<< n->data<< "->";
n = n->next;
}
cout<< "NULL";
return;
}

void insert(node **headref, int n) {
node *temp=new node;

temp->data = n;
temp->next=NULL;
if (last == NULL) {
return;
}
while (last->next)
last = last->next;
last->next = temp;
return;
}

void rotate(node **headref, int k) {
while (k>1){
tempk = tempk->next;
k--;
}
if (tempk == NULL)
return;

node *last = tempk;
while (last->next)
last = last->next;
tempk->next = NULL;
}

int main() {
int n;
while (true) {
cout<< "Enter the number: ";
cin>>n;
if (n==-9)
break;
else