第一章动态规划（六）

例题：12. 背包问题求具体方案

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摘自题解区–"T-SHLoRk "

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
    static int N = 1010; 
    static int[] v = new int[N];
    static int[] w = new int[N];
    static int[][] f = new int[N][N];
    static int n;
    static int m;
    public static void main(String[] args) throws IOException{
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String[] s1 = reader.readLine().split(" ");
        n = Integer.parseInt(s1[0]);
        m = Integer.parseInt(s1[1]);
        for(int i = 1;i <= n;i++) {
            String[] s2 = reader.readLine().split(" ");
            v[i] = Integer.parseInt(s2[0]);
            w[i] = Integer.parseInt(s2[1]);
        }
        //计算状态表示
        for(int i = n;i >= 1;i--) {
            for(int j = 0;j <= m;j++) {
                f[i][j] = f[i + 1][j];
                if(j >= v[i]) {
                    f[i][j] = Math.max(f[i][j], f[i + 1][j - v[i]] + w[i]);
                }
            }
        }
        //f[1][m] 是最大值
        int j = m;
        for(int i = 1;i <= n;i ++) {
            //若当前有选该值则记录
            if(j >= v[i] && f[i][j] == f[i + 1][j - v[i]] + w[i]) {//可以选i
                System.out.print(i + " ");//就必选
                j -= v[i];
            }
        }
    }
}