Discovery | OA | Implement Cash Register
Anonymous User
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Hash TableOrdered SetInterview

Question -

Implement a Cash Register given a bill and amount paid by the customer return the amount of change which has to be provided to the customer.

For Example -

Bill - 100.00

Output - FIFTY DOLLAR,DOLLAR,HALF DOLLAR

Condition

If Bill == amount return "ZERO"
if BILL > amount return "ERROR"

You have to take input from the console and it should run until an input is being given by the user.

Input format - Bill;Amount paid

For Example - 48.50;100.0

My JAVA implementation -

(Why TreeMap instead of HashMap? TreeMap by default stores the keys in a sorted manner, unlike HashMap which stores it randomly)

public static String calculateChange(Double amt, Double bill){
        if(Objects.equals(bill, amt)) return "ZERO";
        if(amt > bill) return "ERROR";

        Double diff = bill - amt;

        Map<Double,String> map = new TreeMap<>(Collections.reverseOrder());

        map.put(100.0, "HUNDRED DOLLAR");
        map.put(50.0, "FIFTY DOLLAR");
        map.put(20.0, "TWENTY DOLLAR");
        map.put(10.0, "TEN DOLLAR");
        map.put(5.0, "FIVE DOLLAR");
        map.put(2.0, "TWO DOLLAR");
        map.put(1.0, "DOLLAR");
        map.put(0.5, "HALF DOLLAR");
        map.put(0.25, "QUARTER");
        map.put(0.1, "DIME");
        map.put(0.05, "FIVE CENT");
        map.put(0.02, "TWO CENT");
        map.put(0.01, "CENT");

        StringBuffer sb = new StringBuffer();

        for(Double curr : map.keySet()){
            if(curr <= diff){
                while(curr <= diff) {
                    if (sb.length() > 1) sb.append(",");
                    sb.append(map.get(curr));
                    diff -= curr;
                }
            }
        }

        return sb.toString();
    }

    public static void main(String[] args) {
       Scanner sc = new Scanner(System.in);
       while (sc.hasNext()){
           String st = sc.nextLine();
           Double amt = Double.valueOf(st.split(";")[0]);
           Double bill = Double.valueOf(st.split(";")[1]);
           System.out.println(calculateChange(amt,bill));
       }
    }

Key Learnings from this OA ?

  1. Many company will ask you to take input and preprocess the data so be prepared for it.
  2. Be proficient in all forms of input method in your language for example in Java you have Scanner & Buffereader, each has their own advantages which you can use in diff circumstances.
  3. Know how to use type casting and conversion.

I was under the impression that I dont have to handle the input (as we have in LeetCode, where we get everything in our function and we simply return the result), so when I saw the question I was confused and did not know how to go about it, I was able to complete the code in 15 - 20 minutes, but I could not figure out how to go about that input part, in such short time I was unable to figure out the input part, so I was unable to run my code over there.

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