朴素做法

#include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;

const int N = 1010;

int n, m;
int v[N], w[N];
int f[N][N];

int main()
{
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; i ++ ) scanf("%d%d", &v[i], &w[i]);

    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] = max(f[i][j], f[i][j - v[i]] + w[i]);
        }

    printf("%d\n", f[n][m]);

    return 0;
}

优化空间做法

#include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;

const int N = 1010;

int n, m;
int v[N], w[N];
int f[N];

int main()
{
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; i ++ ) scanf("%d%d", &v[i], &w[i]);

    for (int i = 1; i <= n;  i++ )
        for (int j = v[i]; j <= m; j ++ )
            f[j] = max(f[j], f[j - v[i]] + w[i]);


    printf("%d\n", f[m]);

    return 0;
}