Fractional knapsack

//Fractional knapsack

import java.io.*;
import java.lang.*;
import java.util.*;

class Item {
    int value, weight;

    Item(int x, int y) {
        this.value = x;
        this.weight = y;
    }
}

class GfG {

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int t = Integer.parseInt(br.readLine().trim());

        while(t-- > 0) {
            String inputLine[] = br.readLine().trim().split(" ");
            int n = Integer.parseInt(inputLine[0]);
            int w = Integer.parseInt(inputLine[1]);
            Item[] arr = new Item[n];
            inputLine = br.readLine().trim().split(" ");

            for(int i = 0, k = 0; i < n; i++) {
                arr[i] = new Item(Integer.parseInt(inputLine[k++]),
                                  Integer.parseInt(inputLine[k++]));
            }
            System.out.println(String.format("%.6f", new Solution().fractionalKnapsack(w, arr, n)));
        }
    }
}

class Item {
    int value, weight;

    Item(int x, int y){
        this.value = x;
        this.weight = y;
    }
}

class itemComparator implements Comparator<Item> {
    @Override
    public int compare(Item a, Item b) {
        double r1 = (double)(a.value) / (double)(a.weight);
        double r2 = (double)(b.value) / (double)(b.weight);
        
        if(r1 < r2) {
            return 1;
        }
        
        else if(r1 > r2) {
            return -1;
        }
        
        else {
            return 0;
        }
    }
}

class Solution {
    double fractionalKnapsack(int w, Item arr[], int n) {
        Arrays.sort(arr, new itemComparator());
        int currW = 0;
        double finalV = 0.0;
        
        for(int i = 0; i < n; i++) {
            if((currW + arr[i].weight) <= w) {
                currW += arr[i].weight;
                finalV += arr[i].value;
            }
            
            else {
                int r = w - currW;
                finalV += ((double)arr[i].value / (double)arr[i].weight) * (double)r;
                break;
            }
        }
        
        return finalV;
    }
}