Interview Question

I came across this question in an interview recently for the SDE-2 position.

There is a shop with old-style cash registers. the price of each item is typed manually. Given a list of items and their correct prices, compare the prices to those entered when each item was sold. Determine the number of errors in the selling price.

Input:
products = ['eggs','milk','cheese']
productPrices = [2.89,3.29,5.79]
productsSold = ['eggs','eggs','milk','cheese']
sellingPrices = [2.89,2.99,3.29,5.97]
Output: errors = 2

Here Comes the Solution for the same.

Use 2 HashMap, one for Storing the original product name and product price, HashMap<String, Float> map2 = new HashMap<String, Float>(); and another for Storing the Selling product name and product price, HashMap<String, ArrayList<Float>> map = new HashMap<String, ArrayList<Float>>(); Here we took Values as a list because there may be multiple selling prices for the same product.

Here is the code for the same.

public static int priceCheck(List<String> products, List<Float> productPrices, List<String> productSold, List<Float> soldPrice) {
    HashMap<String,ArrayList<Float>> map = new HashMap<String,ArrayList<Float>>();
       
        for(int i=0;i<productSold.size();i++){
            String pSold = productSold.get(i);
            if(map.containsKey(pSold)){
                ArrayList<Float> list = map.get(pSold);
                    list.add(soldPrice.get(i));
                map.put(pSold, list);
            }
            else{
                ArrayList<Float> list = new ArrayList<Float>();
                 list.add(soldPrice.get(i));
                map.put(pSold,list);
            }
        }
       HashMap<String,Float> map2 = new HashMap<String,Float>();  
        for(int i=0;i<products.size();i++){
            map2.put(products.get(i), productPrices.get(i));
        }
        
        int error = 0;
        for(Map.Entry<String,Float> map3:map2.entrySet()){
            String pName = map3.getKey();
            Float pCost = map3.getValue();
            if(map.containsKey(pName)){
            ArrayList<Float> price = map.get(pName);
            for(int i=0;i<price.size();i++){
              Float  sCost = price.get(i);
                if(pCost-sCost!=0.0)
                    error++;
                }
            }
        }
        return error;
    }

The code is self-explanatory!

Happy Coding!