Thread: how to add 2 digits?

proper indentation never hurts... Improper indentation like that you are demonstrating - could hurt you severely

scanf("%s",&list1); - no,no,no - no need to & when list1 is already pointer to string (array is pointer to its first element)

you do not need to cast malloc in C - read FAQ

To add to what vart said: you should also free() any memory that you malloc(), or you'll probably end up with some memory leaks.

Indentation suggestion: here's what "indent -kr" spits out. It could be better, but it's better than what you have.

Code:

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


typedef struct node {
    int num;
    struct node *next;
} node, *nodeptr;		//STRUCTURE DECLARED

//FUNCTIONS DECLARED//        

void sl();
nodeptr sum(nodeptr, nodeptr);
nodeptr makenode(int);
void print(nodeptr);
nodeptr makelist(char[]);
nodeptr reverse1(nodeptr);
nodeptr sum(nodeptr, nodeptr);

 //============================================================//     
int main()
{
    char list1[50], list2[50];	//declaration of char array

    nodeptr List1 = NULL, List2 = NULL, sumlist = NULL;


    printf("enter integers for list1 : ");
    scanf("&#37;s", &list1);	//inputs into the array

    printf("Enter integers for List2 : ");
    scanf("%s", &list2);

    List1 = makelist(list1);	//creates a link list with the values from the array
    List2 = makelist(list2);
    sl();
    sl();
    printf("List 1 : ");
    print(List1);
    sl();
    printf("List 2 : ");

    print(List2);
    sl();
    printf("__________________");
    sl();
    printf("SUM    : ");
    print(reverse1(sum(List1, List2)));
    sl();
    sl();

    system("pause");
    return 0;
}

//==================================================//
nodeptr makenode(int n)
{
    nodeptr np = (nodeptr) malloc(sizeof(node));
    np->num = n;
    np->next = NULL;
    return np;
}				//creates a node for the list

//================================================//

void print(nodeptr np)
{
    while (np != NULL) {
	printf("%d", np->num);
	np = np->next;
    }
}

 //==============================================//             
nodeptr makelist(char list1[])
{
    nodeptr makenode(int), np, top, last;
    int i = 0;
    char c = list1[i];		//char at the 1st position of the array
    int n;
    top = NULL;

    while (c != '\0') {		//while char is not the end of the aray
	n = c - '0';		//makes the char into an int
	np = makenode(n);	//makes the node for the int
	if (top == NULL)
	    top = np;
	else
	    last->next = np;
	last = np;

	c = list1[++i];		//increments the list
    }
    return top;
}

 //================================================//                      
void sl()
{
    printf("\n");
}				//just skips a line.


//================================================//
nodeptr reverse1(nodeptr top)
{				//reverses the list

    nodeptr newtop = NULL, temp = NULL;
    while (top != NULL) {
	temp = top;
	top = top->next;
	temp->next = newtop;
	newtop = temp;
    }
    return newtop;
}


//===============================================//
nodeptr sum(nodeptr l1, nodeptr l2)
{
    nodeptr l3 = NULL, last, r1 = NULL, r2 = NULL, np, mp;

    int n, num1, num2, carr = 0;


    r1 = reverse1(l1);		//reverses the list to add the numbers

    r2 = reverse1(l2);


    while (r1 != NULL || r2 != NULL) {
	if (r1 != NULL) {
	    num1 = r1->num;
	    r1 = r1->next;
	} else
	    num1 = 0;
	if (r2 != NULL) {
	    num2 = r2->num;
	    r2 = r2->next;
	} else
	    num2 = 0;

	n = num1 + num2 + carr;
	carr = 0;

	if (n < 10)
	    np = makenode(n);
	else {
	    np = makenode(n - 10);
	    carr = 1;
	}
	if (l3 == NULL)
	    l3 = np;
	else
	    last->next = np;
	last = np;



    }
    if (carr == 1)
	last->next = makenode(carr);


    return l3;
}

Doesn't it seem a little easier to read? . . . .