C Exercises: Add two numbers represented by linked lists

C Singly Linked List : Exercise-22 with Solution

Write a C program that takes two linked lists of numbers. Each node contains a single digit and returns the sum of those numbers of said linked lists as a linked list.

Sample Solution:

C Code:

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

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

// Function to create a new node
struct Node* newNode(int data) {
    struct Node* node = (struct Node*) malloc(sizeof(struct Node));
    node->data = data;
    node->next = NULL;
    return node;
}

// Function to display a linked list
void displayList(struct Node* head) {
    while (head) {
        printf("%d ", head->data);
        head = head->next;
    }
    printf("\n");
}

// Function to add two linked lists
struct Node* add_Lists(struct Node* list1, struct Node* list2) {
    struct Node* res = NULL;
    struct Node* temp, * prev = NULL;
    int carry = 0, sum;

    while (list1 != NULL || list2 != NULL) {
        sum = carry + (list1 ? list1->data : 0) + (list2 ? list2->data : 0);

        carry = (sum >= 10) ? 1 : 0;
        sum = sum % 10;

        temp = newNode(sum);

        if (res == NULL)
            res = temp;
        else
            prev->next = temp;

        prev = temp;

        if (list1) list1 = list1->next;
        if (list2) list2 = list2->next;
    }

    if (carry > 0)
        temp->next = newNode(carry);

    return res;
}

int main() {
    struct Node* list1 = newNode(8);
    list1->next = newNode(7);
    list1->next->next = newNode(9);
    list1->next->next->next = newNode(2);
    printf("List-1\n");
    displayList(list1);
    struct Node* list2 = newNode(2);
    list2->next = newNode(1);
    list2->next->next = newNode(2);
    list2->next->next->next = newNode(3);
    printf("List-2\n");
    displayList(list2);
    struct Node* result = add_Lists(list1, list2);
    printf("\nAdding said two lists:\n");
    displayList(result);
    return 0;
}

Sample Output:

List-1
8 7 9 2 
List-2
2 1 2 3 

Adding said two lists:
0 9 1 6 

Flowchart :

C Programming Code Editor:

Previous: Partition a singly linked list around a specific value.
Next: Rotate a singly linked list to the right by k places.