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-8;
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 = 0;
    while(isdigit(c)) { x = x * 10 + c - '0'; c = getchar(); }
    return x;
}

int sg[200],f[200];

int main()
{
    sg[0]=0;
    for(int i=1;i<=100;i++)
    {
        memset(f,0,sizeof f);

        for(int j=0;j<i;j++) f[sg[j]]=1;

        for(int j=1;j<=i;j++)
        {
            for(int k=1;k<=i;k++)
            {
                for(int s=1;s<=i;s++)
                {
                    if(j+k+s!=i) continue;
                    f[sg[j]^sg[k]^sg[s]]=1;
                }
            }
        }
        for(int j=0;j<200;j++) if(f[j]==0) {sg[i]=j;break;}
    }
    for(int i=0;i<=100;i++) printf("i:%d  sg[i]:%d
",i,sg[i]);
    return 0;
}

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-8;
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 = 0;
    while(isdigit(c)) { x = x * 10 + c - '0'; c = getchar(); }
    return x;
}

const int maxn=1000000+10;
int T,n; LL ans,x;

LL SG(LL x)
{
    if(x==0)return 0; if(x==1) return 1;
    if(x%8==0) return x-1; if((x+1)%8==0) return x+1;
    return x;
}

int main()
{
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d",&n); ans=0;
        for(int i=1;i<=n;i++) scanf("%lld",&x), ans=ans^SG(x);
        if(ans) printf("First player wins.
");
        else printf("Second player wins.
");
    }
    return 0;
}