Day 15 - 货币系统（dp）

考点：DP，背包问题

二维写法：

#include <iostream>

using namespace std;

const int N = 30,M = 10010;
long long f[N][M];

int main()
{
    int n,m;
    cin >> n >> m;
    f[0][0] = 1;
    for(int i = 1; i <= n;  i ++ )
    {
        int v;
        cin >> v;
        
        for(int j = 0; j <= m; j ++ )
        {
            f[i][j] = f[i - 1][j];
            if(j >= v) f[i][j] += f[i][j - v];
        }
    }
    cout << f[n][m] << endl;
    
    return 0;
}
           

一维写法：（空间优化） 

#include <iostream>

using namespace std;

const int N = 30,M = 10010;
long long f[M];

int main()
{
    int n,m;
    cin >> n >> m;
    f[0] = 1;
    for(int i = 1; i <= n;  i ++ )
    {
        int v;
        cin >> v;
        
        for(int j = v; j <= m; j ++ )
        {
            f[j] += f[j - v];
        }
    }
    cout << f[m] << endl;
    
    return 0;
}