HDU 2069 Coin Change

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
//dp[i],最多100枚硬币
const int a[5] = {1, 5, 10, 25, 50};
int main() {
    int n;
    while (cin >> n) {
        ll dp[255][101];  // dp[j][k]:用k个硬币组成j值的个数
        dp[0][0] = 1;
        for (int i = 0; i < 5; i++)
            for (int k = 1; k <= 100; k++)  // k个硬币
                for (int j = a[i]; j <= n; j++) dp[j][k] += dp[j - a[i]][k - 1];
        ll ans = 0;
        for (int i = 0; i <= 100; i++) ans += dp[n][i];
        cout << ans << endl;
    }
    return 0;
}

母函数/完全背包 待了解