GO Classroom(Linked List)

Question

Is my analysis correct?

I analyze code that if it will take 

1->2->3 and 4->1->2 as input

then output will be reverse of 5->3->2 i.e. 2->3->5

Why code is showing runtime error?

#include<stdio.h>
#include<stdlib.h>
#include<ctype.h>
struct node
{
	char digit;
	struct node * next;
};
struct node * makenode(char digit)
{
	struct node *A;
	//int count=0;
	A=NULL;
	struct node *temp=(struct node*)malloc(sizeof(struct node));
	//while(((temp->next)==NULL) && (count<3)){
		//temp=(struct node*)malloc(sizeof(struct node));
		temp->next=digit;
		temp->next=NULL;
		A=temp;
		//count++;
	}
		return 0;
}
 
void printList(struct node * list)
{
	printf("%d->",*list);
}
struct node * readNum()
{
	char c;
	struct node * head, * trav;
	scanf("%c", &c);
	head = trav = makenode(c - '0');//head node creation here
	do
	{
		scanf("%c", &c);
		if(!isdigit(c)) break;
		trav -> next = makenode(c - '0');//more nodes are created and as input is in char, 48 
//subtracted from each node
		trav = trav -> next;
 
	}while(1);
	return head;
}
struct node* reverse(struct node * list, struct node **head)
{
	if(list -> next == NULL)
	{
		*head = list;//head of reversed list;
		return list;
	}
	reverse(list -> next, head) -> next = list;
	list -> next = NULL;
	return list;
}
struct node * simultrav(struct node* trav1, struct node * trav2, char carry)
{
	struct node * temp;
	char sum = carry;
	if(trav1 && trav2)
	{
		sum += trav1 -> digit + trav2 -> digit;
	}
	else if (trav1)
	{
		sum += trav1 -> digit;
	}	
	else if (trav2)
	{
		sum += trav2 -> digit;
	}	
	carry = sum /10;
	sum = sum % 10;
	temp = makenode(sum);
 
	if(trav1  && trav2)
	{
		temp -> next = simultrav(trav1-> next, trav2 -> next, carry);
	}
	else if(trav1)
	{
		temp -> next =  simultrav(trav1-> next, trav2, carry);
	}
	else if(trav2)
	{
		temp -> next =  simultrav(trav1, trav2 -> next, carry);
	}
	else 
	{
		if(carry)
		{
			temp -> next = makenode(carry);
		}
		else
			temp -> next = NULL;
	}
	return temp;
}
 
int main()
{
	struct node * num1, * num2, *rnum1, *rnum2, *sum, *rsum;
	printf("Enter the first number: ");
	num1 = readNum();
	printf("Enter the second number: ");
	num2 = readNum();
	printf("\n");
	reverse( num1, &rnum1);
	reverse( num2, &rnum2);
	rsum = simultrav(rnum1, rnum2, 0);
	reverse( rsum, &sum);
	printf("The sum is : ");
	printList(sum);
	printf("\n");
 return 0;
}

 

Comments

You should return temp in makenode function.

Also, in printList, you should traverse till NULL and print all node values. This was a pretty simple assignment more to familiarize all with linkedlists.

---

Summation of reverse list, is new type question to me, I always getting runtime error.

that is why asked

thank u

---

and why u r subtracting 0?

I understood, as u paased the character in it

but still not clear to me

---

That is to convert char to int. I'm reading digits as char but storing in list as an int of 8 bits size. i.e. say for 2, read value using %c will be its ASCII code 50, but I store the value 50 - 48 = 2 only.

---

yes , I understood now :)

---

 

in makenode()

temp->next=digit;

should be temp->digit= digit

 

in simultrav(),

even though, both lists are completed and carry=0, it will create one more node with value = 0 and make it's next as NULL