uva 1378 博弈

算得上是一个比较复杂的游戏了，解法见论文《解析一类组合游戏》，需要注意的是visit数组要适当开大点防止溢出。

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;

const int N = 25;
int a[N];
int sg[N];

void init()
{
    sg[0] = 0;
    bool visit[N << 1];
    for ( int i = 1; i < N; i++ )
    {
        memset( visit, 0, sizeof(visit) );
        for ( int j = 0; j < i; j++ )
        {
            for ( int k = 0; k <= j; k++ )
            {
                visit[sg[j] ^ sg[k]] = 1;
            }
        }
        int l;
        for ( l = 0; visit[l]; l++ ) ;
        sg[i] = l;
    }
}

int main ()
{
    init();
    int n, _case = 1;
    while ( cin >> n, n )
    {
        int ans = 0;
        for ( int i = 0; i < n; i++ )
        {
            cin >> a[i];
            if ( a[i] & 1 )
            {
                ans = ans ^ sg[n - 1 - i];
            }
        }
        if ( !ans )
        {
            cout << "Game " << _case++ << ": -1 -1 -1" << endl;
        }
        else
        {
            bool flag = false;
            for ( int i = 0; i < n && !flag; i++ )
            {
                if ( !a[i] ) continue;
                for ( int j = i + 1; j < n && !flag; j++ )
                {
                    for ( int k = j; k < n; k++ )
                    {
                        int tmp = ans ^ sg[n - 1 - i] ^ sg[n - 1 - j] ^ sg[n - 1 - k];
                        if ( !tmp )
                        {
                            cout << "Game " << _case++ << ": " << i << ' ' << j << ' ' << k << endl;
                            flag = true;
                            break;
                        }
                    }
                }
            }
        }
    }
    return 0;
}