- Write a C program to print alternate nodes of given linked list.
- Function to print alternate nodes of a linked list.
Given a singly linked list, we have to print all alternate nodes of linked list starting from head node. Check the sample example given below for clarification
Input Linked List 1-->2-->3-->4-->5-->6-->7 Alternate Nodes 1 3 5 7
Algorithm to print alternate nodes of linked list
- Initialize an integer variable "counter" with 0. We will use this variable to track the sequence number of any node from head node. Head node's sequence number is 0.
- Using a while loop, we will traverse linked list from head node till (head != NULL) and increment "counter" variable.
- For every node we will check if value of counter is even(counter%2 == 0) then print current node otherwise continue.
In this program, we will write a user defined function "printAlternateNodes" which implements above mentioned algorithm. printAlternateNodes function takes a pointer to the head node of a linked list and print alternate nodes on screen.
void printAlternateNodes(struct node *head) {
int counter = 0;
printf("\nPrinting Alernate nodes of Linked List\n");
while(head != NULL) {
if (counter%2 == 0) {
printf(" %d ", head->data);
}
counter++;
head = head->next;
}
}
C program to print alternate nodes of a singly linked list
#include <stdio.h>
#include <stdlib.h>
/* A structure of linked list node */
struct node {
int data;
struct node *next;
} *head;
void initialize(){
head = NULL;
}
/*
Given a Inserts a node in front of a singly linked list.
*/
void insert(int num) {
/* Create a new Linked List node */
struct node* newNode = (struct node*) malloc(sizeof(struct node));
newNode->data = num;
/* Next pointer of new node will point to head node of linked list */
newNode->next = head;
/* make new node as new head of linked list */
head = newNode;
printf("Inserted Element : %d\n", num);
}
/* It Prints alternate nodes of a Linked List */
void printAlternateNodes(struct node *head) {
int counter = 0;
printf("\nPrinting Alernate nodes of Linked List\n");
while(head != NULL) {
if (counter%2 == 0) {
printf(" %d ", head->data);
}
counter++;
head = head->next;
}
}
/*
Prints a linked list from head node till tail node
*/
void printLinkedList(struct node *nodePtr) {
while (nodePtr != NULL) {
printf("%d", nodePtr->data);
nodePtr = nodePtr->next;
if(nodePtr != NULL)
printf("-->");
}
}
int main() {
initialize();
/* Creating a linked List*/
insert(7);
insert(6);
insert(5);
insert(4);
insert(3);
insert(2);
insert(1);
printf("\nLinked List\n");
printLinkedList(head);
printAlternateNodes(head);
return 0;
}
OutputInserted Element : 7 Inserted Element : 6 Inserted Element : 5 Inserted Element : 4 Inserted Element : 3 Inserted Element : 2 Inserted Element : 1 Linked List 1-->2-->3-->4-->5-->6-->7 Printing Alernate nodes of Linked List 1 3 5 7