HDU 1581（Number Game）

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int MAXS = 1 << 20;
const int MAXN = 25;

int num[MAXN]; //可选的数
int win[MAXS]; //必胜的状态

//改变状态，根据数字x改变状态s
int changeState(int s, int x)
{
    for (int i = x; i <= 20; i = i + x) //将x的倍数全部置为不可用
    {
        if (s & (1 << (i - 2)))
            s = s & (~(1 << (i - 2)));
    }
    for (int i = 2; i <= 20; i++)
    {
        if (s & (1 << (i - 2)))
        {
            for (int j = x; i - j >= 2; j = j + x)
            {
                if (!(s & (1 << (i - j - 2))))
                {
                    s = s & (~(1 << (i - 2)));
                    break;
                }
            }
        }
    }
    return s;
}

int getSG(int s) 
{
    if (win[s] != -1)
        return win[s];
    int ans = 0;
    for (int i = 2; i <= 20; i++)
    {
        if (s & (1 << (i - 2))) //i存在
        {
            int k = changeState(s, i);
            if (!getSG(k))
                return win[s] = 1;
        }
    }
    return win[s] = 0;
}

int main()
{
    int T;
    cin >> T;
    for (int Case = 1; Case <= T; Case++)
    {
        memset(win, -1, sizeof(win));
        int n;
        cin >> n;
        int state = 0; //可选的数，状态压缩
        for (int i = 0; i < n; i++)
        {
            cin >> num[i];
            state |= (1 << (num[i] - 2));
        }
        sort(num, num + n);
        cout << "Scenario #" << Case << ":" << endl;
        if (!getSG(state))
            cout << "There is no winning move." << endl;
        else 
        {
            cout << "The winning moves are:";
            for (int i = 0; i < n; i++) 
            {
                int s = changeState(state, num[i]);
                if (!getSG(s))
                    cout << " " << num[i];
            }
            cout << "." << endl;
        }
        cout << endl;
    }
    return 0;
}