// Code-A3 (Fractical Knapsack)

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

// Structure for an item
struct Item {
    int weight;
    int value;
};

// Comparison function to sort items by value/weight ratio
bool compare(Item a, Item b) {
    double r1 = (double)a.value / a.weight;
    double r2 = (double)b.value / b.weight;
    return r1 > r2; // Sort in descending order
}

double fractionalKnapsack(int W, vector<Item>& items) {
    // Sort items by value-to-weight ratio
    sort(items.begin(), items.end(), compare);

    double totalValue = 0.0; // Total value in knapsack
    for (auto &i : items) {
        if (W == 0) break; // Knapsack is full

        // If item can be fully taken
        if (i.weight <= W) {
            W -= i.weight;
            totalValue += i.value;
        } else {
            // Take fraction of item
            totalValue += i.value * ((double)W / i.weight);
            W = 0;
        }
    }
    return totalValue;
}

int main() {
    int n, W;
    cout << "Enter number of items: ";
    cin >> n;

    vector<Item> items(n);
    cout << "Enter value and weight of each item:\n";
    for (int i = 0; i < n; i++)
        cin >> items[i].value >> items[i].weight;

    cout << "Enter capacity of knapsack: ";
    cin >> W;

    double maxValue = fractionalKnapsack(W, items);
    cout << "\nMaximum value in knapsack = " << maxValue << endl;

    return 0;
}

// SAMPLE OUTPUT
/*
* $ ./a.out 
* Enter number of items: 3
* Enter value and weight of each item:
* 12 32
* 56 67
* 23 87
* Enter capacity of knapsack: 45
* 
* Maximum value in knapsack = 37.6119
*/