HDU_2069 Coin Change(生成函数)

　　没有看到Your program should be able to handle up to 100 coins. WA了n次。。。处理起来有点麻烦，看到大牛的思路是开一个二维数组c[i][j]，表示用j个硬币组成大小为i的数。把j限定在100以下（有点dp的感觉，呵呵）。就可以了。详见代码：

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

const int N = 250;

int c1[N+1][N+1], c2[N+1][N+1];
int val[5] = {1, 5, 10, 25, 50};

void init() {
    int i, j, k, l;
    memset(c1, 0, sizeof(c1));
    memset(c2, 0, sizeof(c2));

    for(i = 0; i <= N; i++) c1[i][i] = 1;

    for(i = 1; i < 5; ++i) {
        for(j = 0; j <= N; ++j)
            for(k = 0; k*val[i] + j <= N; ++k)
                for(l = 0; l + k <= 100; ++l) {
                    c2[k*val[i] + j][l + k] += c1[j][l];
                }
        for(j = 0; j <= N; ++j)
            for(k = 0; k <= N; ++k) {
                c1[j][k] = c2[j][k]; c2[j][k] = 0;
            }
    }
}

int main() {
    //freopen("data.in", "r", stdin);

    int n, i, sum;
    init();
    while(~scanf("%d", &n)) {
        for(sum = 0, i = 0; i <= n && i <= 100; i++) {
            sum += c1[n][i];
        }
        cout << sum << endl;
    }
    return 0;
}