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;}