04_add-list.c

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

typedef struct list {
        int item;
        struct list *next;
} Node;


Node *list_add(Node *head, int x)
{
        Node *tmp = NULL;

        tmp = (Node *)malloc(sizeof(Node));
        tmp->item = x;

        if (head == NULL) {
                tmp->next = NULL;
        }
        else
                tmp->next = head;

        head = tmp;
        return head;
}

Node *add_lists(Node *l1, Node *l2)
{
        static Node *l3 = NULL;
        int num1, num2, num, digit, carry;

        carry = 0;
        while (l1 != NULL || l2 != NULL) {
                if (l1 == NULL)
                        num1 = 0;
                else
                        num1 = l1->item;

                if (l2 == NULL)
                        num2 = 0;
                else
                        num2 = l2->item;

                num = num1 + num2 + carry;
                digit = num % 10;
                carry = num / 10;
                l3 = list_add(l3, digit);

                if (l1 != NULL) l1 = l1->next;
                if (l2 != NULL) l2 = l2->next;
        }

        if (carry > 0)
                l3 = list_add(l3, carry);

        return l3;
}

void display_list(Node *head)
{
        Node *ptr = NULL;

        for (ptr = head; ptr != NULL; ptr = ptr->next) {
                printf("%d", ptr->item);
        }
        printf("\n");
}

int main()
{
        int i, n;
        char ch;
        char data[50];
        Node *l1 = NULL, *l2 = NULL, *l3 = NULL;

        memset(data, '\0', sizeof(data));
        scanf("%s", data);
        for (i = 0; data[i] != '\0'; i++) {
                ch = data[i];
                l1 = list_add(l1, ch-'0');
        }
        //display_list(l1);

        memset(data, '\0', sizeof(data));
        scanf("%s", data);
        for (i = 0; data[i] != '\0'; i++) {
                ch = data[i];
                l2 = list_add(l2, ch-'0');
        }
        //display_list(l2);

        l3 = add_lists(l1, l2);
        //printf("sum: ");
        display_list(l3);

        return 0;
}