HDU 5795 A Simple Nim

打表找SG函数规律。

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<iostream>
using namespace std;
typedef long long LL;
const double pi=acos(-1.0),eps=1e-;
void File()
{
    freopen("D:\\in.txt","r",stdin);
    freopen("D:\\out.txt","w",stdout);
}
inline int read()
{
    char c = getchar();  while(!isdigit(c)) c = getchar();
    int x = ;
    while(isdigit(c)) { x = x *  + c - ''; c = getchar(); }
    return x;
}

int sg[],f[];

int main()
{
    sg[]=;
    for(int i=;i<=;i++)
    {
        memset(f,,sizeof f);

        for(int j=;j<i;j++) f[sg[j]]=;

        for(int j=;j<=i;j++)
        {
            for(int k=;k<=i;k++)
            {
                for(int s=;s<=i;s++)
                {
                    if(j+k+s!=i) continue;
                    f[sg[j]^sg[k]^sg[s]]=;
                }
            }
        }
        for(int j=;j<;j++) if(f[j]==) {sg[i]=j;break;}
    }
    for(int i=;i<=;i++) printf("i:%d  sg[i]:%d\n",i,sg[i]);
    return ;
}

然后就可以轻松AC了...

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<iostream>
using namespace std;
typedef long long LL;
const double pi=acos(-1.0),eps=1e-;
void File()
{
    freopen("D:\\in.txt","r",stdin);
    freopen("D:\\out.txt","w",stdout);
}
inline int read()
{
    char c = getchar();  while(!isdigit(c)) c = getchar();
    int x = ;
    while(isdigit(c)) { x = x *  + c - ''; c = getchar(); }
    return x;
}

const int maxn=+;
int T,n; LL ans,x;

LL SG(LL x)
{
    if(x==)return ; if(x==) return ;
    if(x%==) return x-; if((x+)%==) return x+;
    return x;
}

int main()
{
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d",&n); ans=;
        for(int i=;i<=n;i++) scanf("%lld",&x), ans=ans^SG(x);
        if(ans) printf("First player wins.\n");
        else printf("Second player wins.\n");
    }
    return ;
}