【暴力预处理+剪枝/bitset】Golf Bot UVALive - 6886

Think:
1知识点：暴力预处理+剪枝/bitset
2题意：输入n个数，查询m次，每次查询输入一个元素，判断这个元素是否可以由最初输入的n个数通过两个数相加或单独一个数得到，两个数相加时可选择同一元素进行相加

vjudge题目链接

以下为Accepted代码——暴力预处理+剪枝-9363ms

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

const int N = 201400;

int a[N], b[N], vis[N<<1];

int main(){
    int n, m, i, j, mav, t, num;
    while(~scanf("%d", &n)){
        mav = 0;
        memset(vis, 0, sizeof(vis));
        for(i = 0; i < n; i++){
            scanf("%d", &a[i]);
            vis[a[i]] = vis[a[i]<<1] = 1;
        }
        scanf("%d", &m);
        for(i = 0; i < m; i++){
            scanf("%d", &b[i]);
            mav = max(mav, b[i]);
        }
        sort(a, a+n);
        for(i = 1; i < n; i++){
            if(a[i] == a[i-1])
                continue;
            for(j = 0; j < i; j++){
                if(a[j]+a[i] > mav)
                    break;
                t = a[j]+a[i];
                vis[t] = 1;
            }
            if(a[i] > mav)
                break;
        }
        num = 0;
        for(i = 0; i < m; i++){
            t = b[i];
            if(vis[t])
                num++;
        }
        printf("%d\n", num);
    }
    return 0;
}

以下为Accepted代码——bitset-4729ms

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <bitset>

using namespace std;

const int N = 201400;

bitset <N> x, y;

int a[N];

int main(){
    int n, i, m, t, num;
    while(~scanf("%d", &n)){
        x.reset();
        y.reset();
        for(i = 0; i < n; i++){
            scanf("%d", &a[i]);
            x[a[i]] = 1;
        }
        y = x;
        for(i = 0; i < n; i++){
            y |= x << a[i];
        }
        scanf("%d", &m);
        num = 0;
        for(i = 0; i < m; i++){
            scanf("%d", &t);
            if(y[t])
                num++;
        }
        printf("%d\n", num);
    }
    return 0;
}