Thread: need qucik help with writing a function

Hi everyone i need help. There are list which are consisting of digits of a number in revers order. For example 456 is in the list like 6 - > 5 -> 4 . I have to write a function which takes two lists like these and add them and write to a new list. For example a list like 2 -> 1 and another like 3 -> 4 -> 2 will reslut two a list like 5 -> 5 -> 2 (12 + 243 = 255 ). I need a qucik help. The fucntion i wrote is always giving errors out.

well this is the code i wrote.

Code:

void addition(int hdr1,int hdr2){
	
	headerArray[hdr2 +1] = (digitNodePtr)malloc(sizeof(digitNode));
	digitNodePtr tmp1 = (digitNodePtr)malloc(sizeof(digitNode));
	digitNodePtr tmp2 = (digitNodePtr)malloc(sizeof(digitNode));
	digitNodePtr tmpLast = (digitNodePtr)malloc(sizeof(digitNode));
	tmp1 = headerArray[hdr1]; //temp pointer to traverse first number
	tmp2 = headerArray[hdr2]; //temp pointer to traverse second number
	
	//the code part for the first digit of the sum list
	digitNodePtr newNodePtr = (digitNodePtr)malloc(sizeof(digitNode));
	headerArray[hdr2 + 1] = newNodePtr;
	tmpLast = headerArray[hdr2 + 1];
	newNodePtr -> digit = (tmp1 -> digit + tmp2 -> digit) % 10;
	if ((tmp1 -> digit + tmp2 -> digit) >= 10 )
		carry = 1;
	else
		carry = 0;
		
	tmp1 = tmp1 -> next;
	tmp2 = tmp2 -> next;
	free(newNodePtr);
	
	//the part to add the other digits to the list 	
	while( tmp2 != NULL ) {
	digitNodePtr newNodePtr = (digitNodePtr)malloc(sizeof(digitNode));
	tmpLast -> next = newNodePtr;
	tmpLast = newNodePtr;
	newNodePtr -> digit = (tmp1 -> digit + tmp2 -> digit + carry) % 10;
	if ((tmp1->digit + tmp2->digit + carry) > 10)
			carry = 1;
		else
			carry = 0;
			
	tmp1 = tmp1 -> next;
	tmp2 = tmp2 -> next;
	free(newNodePtr);
	}
	
	
	//after the add operation if there is a carry it adds 1 at the beginning of the number
	if(carry == 1){
	digitNodePtr newNodePtr = (digitNodePtr)malloc(sizeof(digitNode));
	tmpLast -> next = newNodePtr;
	tmpLast = newNodePtr;
	newNodePtr -> digit = 1;
	free(newNodePtr);
	}
	
}

for example 5 and 6 is a one node list. When i add them 3 becomes the first node of the new sum list. But when trying to assigna newNodePtr's digit to one it doesnt make a new node. Just changes the node 3 's digit to 1 and it becomes a one node list 1. I think it is a problem about this tmpLast or free ing newNodePtr and then malloc it again. Dunno what to do about it.

PS: i use integer parameters because i have a pointer array headerArray[1000] pointing to the lists. Thats why i use index as parameters.

No one can help ???

there is no error. It compiles but i dont get the thing i want

sorry it is because of my english is not that good. I meant it is not working properly when i said The fucntion i wrote is always giving errors out.

hey guys i solved the problem. I know i couldnt tell it. But thx anyway. It is good to know someone there to help me. My problem was using free . I removed it and it is working nice now. .