# Delete every Kth node from circular linked list

Delete every kth Node from a circular linked list until only one node is left. Also print the intermediate lists.

Examples:

```Input : n=4, k=2, list = 1->2->3->4
Output :
1->2->3->4->1
1->2->4->1
2->4->2
2->2

Input : n=9, k=4, list = 1->2->3->4->5->6->7->8->9
Output :
1->2->3->4->5->6->7->8->9->1
1->2->3->4->6->7->8->9->1
1->2->3->4->6->7->8->1
1->2->3->6->7->8->1
2->3->6->7->8->2
2->3->6->8->2
2->3->8->2
2->3->2
2->2
```

Algorithm
Repeat the following steps until there is only one node left in the list.
Case 1: List is empty.
If the list is empty, simply return.

Case 2: List has only one node.
If the list has only one node left, we will print the list and return as our goal is reached.

Case 3: List has more than one nodes.
Define two pointers curr and prev and initialize the pointer curr with the head node.
Traverse the list using curr pointer by iterating it k times.

• Node to be deleted is the first node of the list.
If yes, then move prev until it reaches the last node. After prev reaches the last node, set head = head -> next and prev -> next = head. Delete curr.
• Node to be deleted is the last node in the list.
Condition to check this is (curr -> next == head).
If curr is the last node. Set prev -> next = head and delete the node curr by free(curr).
• Node to be deleted is neither the first node nor the last node, then set prev -> next = temp -> next and delete curr.

## C++

 `// C++ program to delete every kth Node from ` `// circular linked list. ` `#include ` `using` `namespace` `std; ` ` `  `/* structure for a Node */` `struct` `Node { ` `    ``int` `data; ` `    ``Node* next; ` `    ``Node(``int` `x) ` `    ``{ ` `        ``data = x; ` `        ``next = NULL; ` `    ``} ` `}; ` ` `  `/*Utility function to print the circular linked list*/` `void` `printList(Node* head) ` `{ ` `    ``if` `(head == NULL) ` `        ``return``; ` `    ``Node* temp = head; ` `    ``do` `{ ` `        ``cout << temp->data << ``"->"``; ` `        ``temp = temp->next; ` `    ``} ``while` `(temp != head); ` `    ``cout << head->data << endl; ` `} ` ` `  `/*Function to delete every kth Node*/` `void` `deleteK(Node** head_ref, ``int` `k) ` `{ ` `    ``Node* head = *head_ref; ` ` `  `    ``// If list is empty, simply return. ` `    ``if` `(head == NULL) ` `        ``return``; ` ` `  `    ``// take two pointers - current and previous ` `    ``Node *curr = head, *prev; ` `    ``while` `(``true``) { ` ` `  `        ``// Check if Node is the only Node\ ` `        ``// If yes, we reached the goal, therefore  ` `        ``// return. ` `        ``if` `(curr->next == head && curr == head) ` `            ``break``; ` ` `  `        ``// Print intermediate list. ` `        ``printList(head); ` ` `  `        ``// If more than one Node present in the list, ` `        ``// Make previous pointer point to current ` `        ``// Iterate current pointer k times, ` `        ``// i.e. current Node is to be deleted. ` `        ``for` `(``int` `i = 0; i < k; i++) { ` `            ``prev = curr; ` `            ``curr = curr->next; ` `        ``} ` ` `  `        ``// If Node to be deleted is head ` `        ``if` `(curr == head) { ` `            ``prev = head; ` `            ``while` `(prev->next != head) ` `                ``prev = prev->next; ` `            ``head = curr->next; ` `            ``prev->next = head; ` `            ``*head_ref = head; ` `            ``free``(curr); ` `        ``} ` ` `  `        ``// If Node to be deleted is last Node. ` `        ``else` `if` `(curr->next == head) { ` `            ``prev->next = head; ` `            ``free``(curr); ` `        ``} ` `        ``else` `{ ` `            ``prev->next = curr->next; ` `            ``free``(curr); ` `        ``} ` `    ``} ` `} ` ` `  `/* Function to insert a Node at the end of  ` `a Circular linked list */` `void` `insertNode(Node** head_ref, ``int` `x) ` `{ ` `    ``// Create a new Node ` `    ``Node* head = *head_ref; ` `    ``Node* temp = ``new` `Node(x); ` ` `  `    ``// if the list is empty, make the new Node head ` `    ``// Also, it will point to itself. ` `    ``if` `(head == NULL) { ` `        ``temp->next = temp; ` `        ``*head_ref = temp; ` `    ``} ` ` `  `    ``// traverse the list to reach the last Node  ` `    ``// and insert the Node ` `    ``else` `{ ` `        ``Node* temp1 = head; ` `        ``while` `(temp1->next != head) ` `            ``temp1 = temp1->next; ` `        ``temp1->next = temp; ` `        ``temp->next = head; ` `    ``} ` `} ` ` `  `/* Driver program to test above functions */` `int` `main() ` `{ ` `    ``// insert Nodes in the circular linked list ` `    ``struct` `Node* head = NULL; ` `    ``insertNode(&head, 1); ` `    ``insertNode(&head, 2); ` `    ``insertNode(&head, 3); ` `    ``insertNode(&head, 4); ` `    ``insertNode(&head, 5); ` `    ``insertNode(&head, 6); ` `    ``insertNode(&head, 7); ` `    ``insertNode(&head, 8); ` `    ``insertNode(&head, 9); ` ` `  `    ``int` `k = 4; ` ` `  `    ``// Delete every kth Node from the ` `    ``// circular linked list. ` `    ``deleteK(&head, k); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java program to delete every kth Node from  ` `// circular linked list.  ` `class` `GFG ` `{ ` `     `  `/* structure for a Node */` `static` `class` `Node ` `{  ` `    ``int` `data;  ` `    ``Node next;  ` `    ``Node(``int` `x)  ` `    ``{  ` `        ``data = x;  ` `        ``next = ``null``;  ` `    ``}  ` `};  ` ` `  `/*Utility function to print  ` `the circular linked list*/` `static` `void` `printList(Node head)  ` `{  ` `    ``if` `(head == ``null``)  ` `        ``return``;  ` `    ``Node temp = head;  ` `    ``do`  `    ``{  ` `        ``System.out.print( temp.data + ``"->"``);  ` `        ``temp = temp.next;  ` `    ``}  ` `    ``while` `(temp != head);  ` `    ``System.out.println(head.data );  ` `}  ` ` `  `/*Function to delete every kth Node*/` `static` `Node deleteK(Node head_ref, ``int` `k)  ` `{  ` `    ``Node head = head_ref;  ` ` `  `    ``// If list is empty, simply return.  ` `    ``if` `(head == ``null``)  ` `        ``return` `null``;  ` ` `  `    ``// take two pointers - current and previous  ` `    ``Node curr = head, prev=``null``;  ` `    ``while` `(``true``)  ` `    ``{  ` ` `  `        ``// Check if Node is the only Node\  ` `        ``// If yes, we reached the goal, therefore  ` `        ``// return.  ` `        ``if` `(curr.next == head && curr == head)  ` `            ``break``;  ` ` `  `        ``// Print intermediate list.  ` `        ``printList(head);  ` ` `  `        ``// If more than one Node present in the list,  ` `        ``// Make previous pointer point to current  ` `        ``// Iterate current pointer k times,  ` `        ``// i.e. current Node is to be deleted.  ` `        ``for` `(``int` `i = ``0``; i < k; i++)  ` `        ``{  ` `            ``prev = curr;  ` `            ``curr = curr.next;  ` `        ``}  ` ` `  `        ``// If Node to be deleted is head  ` `        ``if` `(curr == head)  ` `        ``{  ` `            ``prev = head;  ` `            ``while` `(prev.next != head)  ` `                ``prev = prev.next;  ` `            ``head = curr.next;  ` `            ``prev.next = head;  ` `            ``head_ref = head;  ` `        ``}  ` ` `  `        ``// If Node to be deleted is last Node.  ` `        ``else` `if` `(curr.next == head)  ` `        ``{  ` `            ``prev.next = head;  ` `        ``}  ` `        ``else` `        ``{  ` `            ``prev.next = curr.next;  ` `        ``}  ` `    ``}  ` `    ``return` `head; ` `}  ` ` `  `/* Function to insert a Node at the end of  ` `a Circular linked list */` `static` `Node insertNode(Node head_ref, ``int` `x)  ` `{  ` `    ``// Create a new Node  ` `    ``Node head = head_ref;  ` `    ``Node temp = ``new` `Node(x);  ` ` `  `    ``// if the list is empty, make the new Node head  ` `    ``// Also, it will point to itself.  ` `    ``if` `(head == ``null``)  ` `    ``{  ` `        ``temp.next = temp;  ` `        ``head_ref = temp;  ` `        ``return` `head_ref; ` `    ``}  ` ` `  `    ``// traverse the list to reach the last Node  ` `    ``// and insert the Node  ` `    ``else`  `    ``{  ` `        ``Node temp1 = head;  ` `        ``while` `(temp1.next != head)  ` `            ``temp1 = temp1.next;  ` `        ``temp1.next = temp;  ` `        ``temp.next = head;  ` `    ``}  ` `    ``return` `head; ` `}  ` ` `  `/* Driver code */` `public` `static` `void` `main(String args[]) ` `{  ` `    ``// insert Nodes in the circular linked list  ` `    ``Node head = ``null``;  ` `    ``head = insertNode(head, ``1``);  ` `    ``head = insertNode(head, ``2``);  ` `    ``head = insertNode(head, ``3``);  ` `    ``head = insertNode(head, ``4``);  ` `    ``head = insertNode(head, ``5``);  ` `    ``head = insertNode(head, ``6``);  ` `    ``head = insertNode(head, ``7``);  ` `    ``head = insertNode(head, ``8``);  ` `    ``head = insertNode(head, ``9``);  ` ` `  `    ``int` `k = ``4``;  ` ` `  `    ``// Delete every kth Node from the  ` `    ``// circular linked list.  ` `    ``head = deleteK(head, k);  ` `}  ` `} ` ` `  `// This code is contributed by Arnab Kundu `

## Python3

 `# Python3 program to delete every kth Node from ` `# circular linked list. ` `import` `math ` ` `  `# structure for a Node  ` `class` `Node:  ` `    ``def` `__init__(``self``, data):  ` `        ``self``.data ``=` `data  ` `        ``self``.``next` `=` `None` ` `  `# Utility function to print the circular linked list ` `def` `prList(head): ` `    ``if` `(head ``=``=` `None``): ` `        ``return` `    ``temp ``=` `head ` `     `  `    ``print``(temp.data, end ``=` `"->"``) ` `    ``temp ``=` `temp.``next` `    ``while` `(temp !``=` `head): ` `        ``print``(temp.data, end ``=` `"->"``) ` `        ``temp ``=` `temp.``next` `    ``print``(head.data) ` ` `  `# Function to delete every kth Node ` `def` `deleteK(head_ref, k): ` `    ``head ``=` `head_ref ` ` `  `    ``# If list is empty, simply return. ` `    ``if` `(head ``=``=` `None``): ` `        ``return` ` `  `    ``# take two poers - current and previous ` `    ``curr ``=` `head ` `    ``prev ``=` `None` `    ``while` `True``: ` ` `  `        ``# Check if Node is the only Node\ ` `        ``# If yes, we reached the goal, therefore  ` `        ``# return. ` `        ``if` `(curr.``next` `=``=` `head ``and` `curr ``=``=` `head): ` `            ``break` ` `  `        ``# Pr intermediate list. ` `        ``prList(head) ` ` `  `        ``# If more than one Node present in the list, ` `        ``# Make previous pointer po to current ` `        ``# Iterate current pointer k times, ` `        ``# i.e. current Node is to be deleted. ` `        ``for` `i ``in` `range``(k): ` `            ``prev ``=` `curr ` `            ``curr ``=` `curr.``next` ` `  `        ``# If Node to be deleted is head ` `        ``if` `(curr ``=``=` `head): ` `            ``prev ``=` `head ` `            ``while` `(prev.``next` `!``=` `head): ` `                ``prev ``=` `prev.``next` `            ``head ``=` `curr.``next` `            ``prev.``next` `=` `head ` `            ``head_ref ``=` `head ` ` `  `        ``# If Node to be deleted is last Node. ` `        ``elif` `(curr.``next` `=``=` `head) : ` `            ``prev.``next` `=` `head ` `             `  `        ``else` `: ` `            ``prev.``next` `=` `curr.``next` ` `  `# Function to insert a Node at the end of  ` `#a Circular linked list  ` `def` `insertNode(head_ref, x): ` `     `  `    ``# Create a new Node ` `    ``head ``=` `head_ref ` `    ``temp ``=` `Node(x) ` ` `  `    ``# if the list is empty, make the new Node head ` `    ``# Also, it will po to itself. ` `    ``if` `(head ``=``=` `None``): ` `        ``temp.``next` `=` `temp ` `        ``head_ref ``=` `temp ` `        ``return` `head_ref ` `     `  `    ``# traverse the list to reach the last Node  ` `    ``# and insert the Node ` `    ``else` `: ` `        ``temp1 ``=` `head ` `        ``while` `(temp1.``next` `!``=` `head): ` `            ``temp1 ``=` `temp1.``next` `        ``temp1.``next` `=` `temp ` `        ``temp.``next` `=` `head ` `    ``return` `head ` ` `  `# Driver Code ` `if` `__name__``=``=``'__main__'``: ` `     `  `    ``# insert Nodes in the circular linked list ` `    ``head ``=` `None` `    ``head ``=` `insertNode(head, ``1``)  ` `    ``head ``=` `insertNode(head, ``2``)  ` `    ``head ``=` `insertNode(head, ``3``)  ` `    ``head ``=` `insertNode(head, ``4``)  ` `    ``head ``=` `insertNode(head, ``5``)  ` `    ``head ``=` `insertNode(head, ``6``)  ` `    ``head ``=` `insertNode(head, ``7``)  ` `    ``head ``=` `insertNode(head, ``8``)  ` `    ``head ``=` `insertNode(head, ``9``)  ` ` `  `    ``k ``=` `4` ` `  `    ``# Delete every kth Node from the ` `    ``# circular linked list. ` `    ``deleteK(head, k) ` ` `  `# This code is contributed by Srathore `

## C#

 `// C# program to delete every kth Node from  ` `// circular linked list. ` `using` `System; ` ` `  `class` `GFG ` `{ ` `     `  `/* structure for a Node */` `public` `class` `Node ` `{  ` `    ``public` `int` `data;  ` `    ``public` `Node next;  ` `    ``public` `Node(``int` `x)  ` `    ``{  ` `        ``data = x;  ` `        ``next = ``null``;  ` `    ``}  ` `};  ` ` `  `/*Utility function to print  ` `the circular linked list*/` `static` `void` `printList(Node head)  ` `{  ` `    ``if` `(head == ``null``)  ` `        ``return``;  ` `    ``Node temp = head;  ` `    ``do` `    ``{  ` `        ``Console.Write( temp.data + ``"->"``);  ` `        ``temp = temp.next;  ` `    ``}  ` `    ``while` `(temp != head);  ` `    ``Console.WriteLine(head.data );  ` `}  ` ` `  `/*Function to delete every kth Node*/` `static` `Node deleteK(Node head_ref, ``int` `k)  ` `{  ` `    ``Node head = head_ref;  ` ` `  `    ``// If list is empty, simply return.  ` `    ``if` `(head == ``null``)  ` `        ``return` `null``;  ` ` `  `    ``// take two pointers - current and previous  ` `    ``Node curr = head, prev = ``null``;  ` `    ``while` `(``true``)  ` `    ``{  ` ` `  `        ``// Check if Node is the only Node\  ` `        ``// If yes, we reached the goal, therefore  ` `        ``// return.  ` `        ``if` `(curr.next == head && curr == head)  ` `            ``break``;  ` ` `  `        ``// Print intermediate list.  ` `        ``printList(head);  ` ` `  `        ``// If more than one Node present in the list,  ` `        ``// Make previous pointer point to current  ` `        ``// Iterate current pointer k times,  ` `        ``// i.e. current Node is to be deleted.  ` `        ``for` `(``int` `i = 0; i < k; i++)  ` `        ``{  ` `            ``prev = curr;  ` `            ``curr = curr.next;  ` `        ``}  ` ` `  `        ``// If Node to be deleted is head  ` `        ``if` `(curr == head)  ` `        ``{  ` `            ``prev = head;  ` `            ``while` `(prev.next != head)  ` `                ``prev = prev.next;  ` `            ``head = curr.next;  ` `            ``prev.next = head;  ` `            ``head_ref = head;  ` `        ``}  ` ` `  `        ``// If Node to be deleted is last Node.  ` `        ``else` `if` `(curr.next == head)  ` `        ``{  ` `            ``prev.next = head;  ` `        ``}  ` `        ``else` `        ``{  ` `            ``prev.next = curr.next;  ` `        ``}  ` `    ``}  ` `    ``return` `head; ` `}  ` ` `  `/* Function to insert a Node at the end of  ` `a Circular linked list */` `static` `Node insertNode(Node head_ref, ``int` `x)  ` `{  ` `    ``// Create a new Node  ` `    ``Node head = head_ref;  ` `    ``Node temp = ``new` `Node(x);  ` ` `  `    ``// if the list is empty, make the new Node head  ` `    ``// Also, it will point to itself.  ` `    ``if` `(head == ``null``)  ` `    ``{  ` `        ``temp.next = temp;  ` `        ``head_ref = temp;  ` `        ``return` `head_ref; ` `    ``}  ` ` `  `    ``// traverse the list to reach the last Node  ` `    ``// and insert the Node  ` `    ``else` `    ``{  ` `        ``Node temp1 = head;  ` `        ``while` `(temp1.next != head)  ` `            ``temp1 = temp1.next;  ` `        ``temp1.next = temp;  ` `        ``temp.next = head;  ` `    ``}  ` `    ``return` `head; ` `}  ` ` `  `/* Driver code */` `public` `static` `void` `Main(String []args) ` `{  ` `    ``// insert Nodes in the circular linked list  ` `    ``Node head = ``null``;  ` `    ``head = insertNode(head, 1);  ` `    ``head = insertNode(head, 2);  ` `    ``head = insertNode(head, 3);  ` `    ``head = insertNode(head, 4);  ` `    ``head = insertNode(head, 5);  ` `    ``head = insertNode(head, 6);  ` `    ``head = insertNode(head, 7);  ` `    ``head = insertNode(head, 8);  ` `    ``head = insertNode(head, 9);  ` ` `  `    ``int` `k = 4;  ` ` `  `    ``// Delete every kth Node from the  ` `    ``// circular linked list.  ` `    ``head = deleteK(head, k);  ` `}  ` `} ` ` `  `// This code has been contributed by 29AjayKumar `

Output:

```1->2->3->4->5->6->7->8->9->1
1->2->3->4->6->7->8->9->1
1->2->3->4->6->7->8->1
1->2->3->6->7->8->1
2->3->6->7->8->2
2->3->6->8->2
2->3->8->2
2->3->2
2->2
```

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