AcWing 12. 背包问题求具体方案

Posted 2020-11-23 qingyuyyyyy

//f[i][j]=max(f[i-1][j],f[i-1][j-v[i]]+w[i]) 
#include <iostream>
using namespace std;
const int N = 1010;
int n, m;
int v[N], w[N];
int f[N][N];
int main() {
    cin >> n >> m;
    for (int i = 1; i <= n; i ++ ) cin >> v[i] >> w[i];
    for (int i = n; i >= 1; i -- )//最小字典序，从前往后推，那么做dp的时候，从后往前 
        for (int j = 0; j <= m; j ++ ) {//由于状态是两维的，所以循环顺序无所谓 
            f[i][j] = f[i + 1][j];
            if (j >= v[i]) f[i][j] = max(f[i][j], f[i + 1][j - v[i]] + w[i]);
        }
    //f[1][m]是最大价值 
    int j = m;
    for (int i = 1; i <= n; i ++ )//依次看每个物品能不能选 
            //保证后面大于等于0 
        if (j >= v[i] && f[i][j] == f[i + 1][j - v[i]] + w[i]) {//只要可以选，就必选 
            cout << i << ‘ ‘;
            j -= v[i];
        }
    return 0;
}