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POJ-1143

给定一个序列，轮到谁，取出一个数k删除,并删除i*k(i=1,2,3,.....),

设k1为已经删除的数，同时删除k1*i+k*j,(i=1,2,3,.....;j同上 )，轮到谁没数删除时谁就输了。。

求先手取数可以取那些数字，能保证获胜

#include<iostream>
#include <cstring>
#include <algorithm>
#include <iomanip>
#define IOS std::ios::sync_with_stdio(false);std::cin.tie(0);
using namespace std ;
const int N =(1<<20)+20;
 int f[N] ;
 int b[N]; 
 bool dfs(int s,int x){
    s-=(1<<x) ;
    for(int i=2;i+x<=20;i++)
        if ( !((1<<i)&s) && (1<<(i+x))&s )
            s-=(1<<(i+x));
             
    if(f[s]>0) return 1 ;
    if(f[s]<0) return 0;
     
    for(int i=2;i<=20;i++)
        if( (1<<i)&s&&!dfs(s,i)){
            return f[s]=1 ;
        }
     
    f[s]=-1 ;
    return 0 ;
 }
 signed main(){
    int n,v,k,cnt=1,flag=0;
    while (cin>>n&&n){
        k=0;
        if (flag)
            cout<<endl;
        memset(f,0,sizeof f);
        f[0]=-1;
        int ans=0;
        for (int i=0;i<n;i++){
            cin>>v;
            ans+=(1<<v);
        }
        for (int i=2;i<=20;i++)
            if(((1<<i)&ans)&&!dfs(ans,i))
                b[k++]=i;
        sort(b,b+k);
        k=unique(b,b+k)-b;
         
        cout<<"Test Case #"<<cnt++<<endl;
        if (k)
        {
            cout<<"The winning moves are: "; 
            for (int i=0;i<k;i++)
                cout<<b[i] << ((i==k-1)?"\n":" ");
        }
        else
            cout<<"There's no winning move."<<endl;
        flag=1;
    }
    return 0;
} 