Home Work Problem.

I understand what the program is suppose to do, but I do not understand how to implement it using Link List.

Please help me to understand the problem.

Write a program to perform ariththmetic with integers of unlimited size. You must read data from the input file, input.txt and send output to the file, output.txt.

Each data line has the following format:

number1 operator number 2, where the operator can be one of +, - or *. The operator is preceeded and followed by one or more spaces.

For + and -, Number1 and Number 2 are to be treated as large integers and each must be stored in a link list. Output the given expression and on the next line print the answer. For example,

22222233333333 + 4444455555 =

For *, Number1 is a large integer to be stored in a linked list. Number2 is a small integer whcih can be stored in an int variable. Output the given expression ans on the next line, print the answer for example,

23222222222222 * 7 =

223232323223333

the last line of data contains a zero.

Please help me to under the algorithm in solving this problem

Code:

Class Node {
Int num;
Node next;
}
Public Class Number {
Public static void main (String [] args) {
Scanner in = new Scanner (new File Reader (“input.txt”)
PrinterWriter out = new PrintWriter (new FileWriter (“output.txt”)
Node top, last, np = null;
top = null;
// Load the input file into the link list
int n = in.nextInt()
While (n! =0) {
np = new node (num)
if (top = = null) {
top = np;
else {
last.next = np;
num = in.nextInt ()
}
}
Curr = top
While (curr !=Null)
String sign = in.next()
If (sign. equals (‘+’) {
Int sum = prev.next +curr.next
Curr = curr.next
//write to output file
Elseif{
If (sign. equals (‘-’) {
Int difference = prer.next -curr.next
Curr = curr.next
//write to output file
}
Else{
If (sign. equals (‘*’) {
Int product = curr.num *curr.next
Curr = curr.next
//write to output file
}