完全背包求方案数

import java.util.*;

public class Main {
    static final int N = 20, M = 3010;
    static long[][] f = new long[N][M];
    static int[] v = new int[N];
    static int n, m;

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        m = sc.nextInt();

        for (int i = 1; i <= n; i++) v[i] = sc.nextInt();

        for (int i = 0; i <= n; i++) f[i][0] = 1;
        for (int i = 1; i <= n; i++)
            for (int j = 1; j <= m; j++) {
                for (int k = 0; k * v[i] <= j; k++) 
                    f[i][j] += f[i - 1][j - k * v[i]];
            }

        System.out.println(f[n][m]);
    }
}

import java.util.*;

public class Main {
    static final int N = 20, M = 3010;
    static long[][] f = new long[N][M];
    static int[] v = new int[N];
    static int n, m;

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        m = sc.nextInt();

        for (int i = 1; i <= n; i++) v[i] = sc.nextInt();

        for (int i = 0; i <= n; i++) f[i][0] = 1;
        for (int i = 1; i <= n; i++)
            for (int j = 1; j <= m; j++) {
                f[i][j] = f[i - 1][j];
                if (j >= v[i])
                    f[i][j] += f[i][j - v[i]];                
            }

        System.out.println(f[n][m]);
    }
}

import java.util.*;

public class Main {
    static final int N = 20, M = 3010;
    static long[] f = new long[M];
    static int[] v = new int[N];
    static int n, m;

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        m = sc.nextInt();

        for (int i = 1; i <= n; i++) v[i] = sc.nextInt();

        f[0] = 1;
        for (int i = 1; i <= n; i++)
            for (int j = 1; j <= m; j++)
                if (j >= v[i])
                    f[j] += f[j - v[i]];                

        System.out.println(f[m]);
    }
}

import java.util.*;

public class Main {
    static final int N = 20, M = 3010;
    static long[] f = new long[M];
    static int n, m;

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        m = sc.nextInt();

        f[0] = 1;
        for (int i = 1; i <= n; i++) {
            int v = sc.nextInt();
            for (int j = v; j <= m; j++)
                f[j] += f[j - v];                
        }

        System.out.println(f[m]);
    }
}