C Exercises: Interleave elements of two linked lists alternatively

C Singly Linked List : Exercise-39 with Solution

Write a C program to interleave elements of two singly linked lists alternatively.

Sample Solution:

C Code:

#include<stdio.h>
#include <stdlib.h>

struct Node {
    int data;
    struct Node* next;
};

// Function to insert a new node at the end of a linked list
void append_data(struct Node** head, int data) {
    struct Node* new_node = (struct Node*) malloc(sizeof(struct Node));
    new_node->data = data;
    new_node->next = NULL;
    
    if (*head == NULL) {
        *head = new_node;
    } else {
        struct Node* last = *head;
        while (last->next != NULL) {
            last = last->next;
        }
        last->next = new_node;
    }
}

// Function to interleave elements of two linked lists alternatively
void interleave(struct Node** head1, struct Node** head2) {
    if (*head1 == NULL || *head2 == NULL) {
        return;
    }

    struct Node* curr1 = *head1;
    struct Node* curr2 = *head2;

    while (curr1 != NULL && curr2 != NULL) {
        struct Node* temp1 = curr1->next;
        struct Node* temp2 = curr2->next;

        curr1->next = curr2;
        curr2->next = temp1;

        curr1 = temp1;
        curr2 = temp2;
    }
}


// Function to print a linked list
void printList(struct Node* node) {
    while (node != NULL) {
        printf("%d ", node->data);
        node = node->next;
    }
}
int main() {
    struct Node* head1 = NULL;
    struct Node* head2 = NULL;
    
    // Add some nodes to the first linked list
    append_data(&head1, 1);
    append_data(&head1, 3);
    append_data(&head1, 5);
    append_data(&head1, 7);
    
    // Add some nodes to the second linked list
    append_data(&head2, 2);
    append_data(&head2, 4);
    append_data(&head2, 6);
    append_data(&head2, 8);
    printf("Original Lists:\n");
    printf("List1: ");
    printList(head1);
    printf("\nList2: ");
    printList(head2);
    
    // Interleave the two linked lists alternatively
    interleave(&head1, &head2);
    printf("\n\nAfter interleaving the two linked lists alternatively:\n");
    printf("List1: ");
    printList(head1);
    printf("\nList2: ");
    printList(head2);    
    return 0;
}

Sample Output:

Original Lists:
List1: 1 3 5 7 
List2: 2 4 6 8 

After interleaving the two linked lists alternatively:
List1: 1 2 3 4 5 6 7 8 
List2: 2 3 4 5 6 7 8 

Flowchart :

C Programming Code Editor:

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