题目描述

dp(不存负数，所以就多一倍)

样例

import java.util.*;
public class Main{

    static int N = 110, M = 200010, B = M / 2;

    static int n, m;
    static int w[] = new int[N];
    static boolean f[][] = new boolean[N][M];

    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        for (int i = 1; i <= n; i ++ ){
            w[i] = sc.nextInt();
            m += w[i];
        }

        f[0][B] = true;
        for(int i = 1; i <= n;i ++){
            for(int j = -m; j <= m; j ++){
                //不选
                f[i][j + B] = f[i - 1][j + B];
                //正选
                if (j - w[i] >= -m) f[i][j + B] |= f[i - 1][j - w[i] + B];
                //负选
                if (j + w[i] <= m) f[i][j + B] |= f[i - 1][j + w[i] + B];
            }
        }

        int res = 0;
        for (int j = 1; j <= m; j ++ ){
            if (f[n][j + B]){
                res ++ ;
            }

        }


        System.out.println(res);
    }
}