Project Euler：Problem 31 Coin sums

In England the currency is made up of pound, ￡, and pence, p, and there are eight coins in general circulation:

1p, 2p, 5p, 10p, 20p, 50p, ￡1 (100p) and ￡2 (200p).

It is possible to make ￡2 in the following way:

1×￡1 + 1×50p + 2×20p + 1×5p + 1×2p + 3×1p

How many different ways can ￡2 be made using any number of coins?

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

int compute(int f, vector<int> a)
{
	if (a.size() == 0 || f < 0)
		return 0;
	if (f == 0 || a.size() == 1)
		return 1;
	else
	{
		int largest;
		largest = a[a.size() - 1];
		int uses = f / largest;
		int count = 0;
		if (a.size() >= 1)
			a.pop_back();
		for (int i = 0; i <= uses; i++)
				count += compute(f - largest*i, a);
		return count;
	}
}

int main()
{
	int f = 200;
	int a[8] = { 1, 2, 5, 10, 20, 50, 100, 200 };
	vector<int>coins(a, a + 8);
	cout << compute(f, coins) << endl;
	system("pause");
	return 0;
}