Greedy Knapsack Problem - Implementation

#include <bits/stdc++.h>
using namespace std;
struct Item {
	int value, weight;
	Item(int value, int weight)
	{
    	this->value=value;
	    this->weight=weight;
	}
};
bool cmp(struct Item a, struct Item b)
{
	double r1 = (double)a.value / (double)a.weight;
	double r2 = (double)b.value / (double)b.weight;
	return r1 > r2;
}
double fractionalKnapsack(int W, struct Item arr[], int n)
{
	sort(arr, arr + n, cmp);
	int curWeight = 0; // Current weight in knapsack
	double finalvalue = 0.0; // Result (value in Knapsack)
	for (int i = 0; i < n; i++) {
		if (curWeight + arr[i].weight <= W) {
			curWeight += arr[i].weight;
			finalvalue += arr[i].value;
		}
		else {
			int remain = W - curWeight;
			finalvalue += arr[i].value * ((double)remain / (double)arr[i].weight);
			break;
		}
	}
	return finalvalue;
}
int main()
{
	int W = 50; 
	Item arr[] = { { 60, 10 }, { 100, 20 }, { 120, 30 } };
	int n = sizeof(arr) / sizeof(arr[0]);
	cout << "Maximum Profit we can obtain = " << fractionalKnapsack(W, arr, n);
	return 0;
}