C program reversed linked list - c

Question

Im trying to write a program in c that adds big numbers with linked list. I used reverse to add the numbers, but i cant get it to reverse again. It should be used several times(iow, looped to ask numbers until exit)
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "function.c"
int main()
{
char n1[500];
int lenSum, len;
printf("Welcome! \nThis program performs addition of big whole numbers that can contain upto a maximum of 500 digits.");
printf("\nEnter first number: ");
scanf("%s", n1);
len = strlen(n1);
node *root = create(n1[0]);
node *head = root;
root, head = createList(n1,root,head,len);
root=head;
printf("Enter second number: ");
scanf("%s", n1);
len = strlen(n1);
node *root2 = create(n1[0]);
node *head2 = root2;
root2, head2 = createList(n1,root2,head2,len);
root2=head2;
root=head;
printf("\nYour first number is:\t ");
while(root!=NULL){
printf("%d\t",root->digit);
root=root->next;
}
root2=head2;
printf("\nYour second number is: ");
while(root2!=NULL){
printf("%d\t",root2->digit);
root2=root2->next;
}
printf("\nCalculating sum:\n");
root=head;
root2=head2;
node *sum = create('0');
node *headSum = sum;
sum,headSum = addIntegers(root, root2, sum, headSum);
printf("\nThe sum is : ");
sum=headSum;
while(sum->next!=NULL){
printf("%d",sum->digit);
sum=sum->next;
}
printf("\n");
sum = headSum;
printf("\nThe number ");
saveResult(sum);
printf("has been saved in the file 'results.txt'\n");
root, head = reverseLinkedList(sum, headSum);
printDigit(root);
root=head;
printf("\n\n\t ");
while(root!=NULL){
printf("%d\t",root->digit);
root=root->next;
}
free(root);
free(root2);
//free(sumDigit);//
return 0;
}
function.h:
#ifndef function.h
#define function.h
typedef struct node {
int digit;
struct node *next;
}node;
node* create(char digit);
node* createList(char number[500], node* root,node* head, int length);
node* addIntegers(node* root, node* root2, node* sum, node* headSum);
#endif
function.c:
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "function.h"
node* createList(char number[500], node* root,node* head, int length){
int i;
i=0;
for(i=1;i<=length-1;i++) {
root = (node *)malloc(sizeof(node));
root->digit = number[i]-'0';
root->next = head;
head = root;
}
return root, head;
}
void printDigit(node* root){
while(root!=NULL){
printf("%d",root->digit);
root=root->next;
}
}
node* addIntegers(node* root, node* root2, node* sum, node* headSum){
int carry = 0;
int sumDigit = 0;
while((root!=NULL || root2!=NULL)) {
if (root==NULL || root2==NULL){
if (root == NULL){
sumDigit=root2->digit +carry;
root2=root2->next;
goto add;}
if (root2 == NULL){
sumDigit = root->digit + carry;
root=root->next;
goto add;
}
}
else{
sumDigit = root->digit + root2-> digit + carry;
}
root2 = root2->next;
root = root->next;
add:
sum = (node *)malloc(sizeof(node));
sum->digit = sumDigit%10;
sum->next = headSum;
headSum = sum;
if (sumDigit > 9){
carry = 1;}
else{
carry = 0;
}
}
if (carry == 1){
sum = (node *)malloc(sizeof(node));
sum->digit = 1;
sum->next = headSum;
headSum = sum;
}
return sum, headSum;
}
node* create(char digit)
{
node *root = (node *) malloc( sizeof(node));
if (root == NULL){
printf("ERROR\n");
exit(1);
}
root->digit = digit-'0';
root->next = NULL; //default is null
return root;
}
void saveResult(struct node *sum)
{
FILE * fp = fopen ("result.txt", "w+");
while(sum->next != NULL)
{
printf("%d", sum->digit);
fprintf(fp, "%d", sum->digit);
sum = sum->next;
}
fclose(fp);
printf(" ");
}
node* reverseLinkedList(node *root, node* head){
node* reversed = create(root->digit);
node* reversedTail = reversed;
while(root!=NULL){
//printf("%d", root->digit);
root = root->next;
reversed->digit = root;
reversed->next =head->next;
reversed = reversed->next;
head = root;
}
reversed = reversedTail;
return reversed, reversedTail;
}

Answer 1

As the question is not very specific with the issue you're are facing, below are some points to be taken care,
In function reverse(),
return reversed, reversedTail; will always return reversedTail.
You are trying to call this function from main() as
root, head = reverseLinkedList(sum, headSum); which again head will get the return values. This is incorrect. Usually you should be using a assignment to one member at a time.

Answer 2

link list reverse sample like this
#include <stdio.h>
#include <stdlib.h>
typedef struct node {
int digit;
struct node *next;
} node;
node *reverse_copy(node *list){
node *new_list = NULL;
while(list){
node *new_node = malloc(sizeof(node));
new_node->digit = list->digit;
new_node->next = new_list;
new_list = new_node;
list = list->next;
}
return new_list;
}
void reverse_not_copy(node **header){
node *tmp, *list, *newList = NULL;
if (header==NULL || *header == NULL) return;
list = *header;
while(list != NULL){
tmp = list;
list = list->next;
tmp->next = newList;
newList = tmp;
}
*header = newList;
}
void print(node *head){
while(head){
printf("%d ", head->digit);
head = head->next;
}
printf("\n");
}
int main(void){
node *np;
node n[3] = { {1,NULL}, {2, NULL}, {3, NULL}};
n[0].next = &n[1];
n[1].next = &n[2];
print(&n[0]);//1 2 3
np=reverse_copy(&n[0]);
print(np);//3 2 1
reverse_not_copy(&np);
print(np);//1 2 3
return 0;
}