题目大意;

给一个字符串，长度6以内，由0~9组成,有两个操作,每次进行一个, 把任意位上的非0的数变成一个比他小的数,

例如1256 ,对5操作,把5变成 0,1,2,3,4,中任意一个,如果该位为0,则删除该位及后面所有位.

sg 暴力dfs

#include <cstdio>
#include <cstring>
#include <cmath>
#include <istream>
using namespace std;

const int maxn = 1000500;
char str[10];
int sg[maxn];

///得到n个0
inline int getten(int i){
    switch(i){
    case 1:return 1;
    case 2:return 10;
    case 3:return 100;
    case 4:return 1000;
    case 5:return 10000;
    case 6:return 100000;
    case 7:return 1000000;
    }
    return 1;
}
inline int getNpos(int x,int const &pos){
    x %= getten(pos+1);
    x /= getten(pos);
    return x;
}
int DFS(int const &state){
    //如果已经判断过了
    if (sg[state] != -1) return  sg[state];
    //N状态
    if (state == 0) return 1;
    int t_state = state;
    //得到位数
    int l = 0;
    while(t_state)
        l++,t_state /= 10;

    for (int i = l;i >= 1;--i){

        t_state = state;
        const int temp = getNpos(state,i);
        if (temp){
            //该位上的数依次减1
            for (int j = 1;j < temp;++j){
                 t_state -= getten(i);
                //能得到P状态,说明此时是N状态
                if ( DFS(t_state) == 0){
                    t_state+= j*getten(i);
                    return 1;
                }
            }
            //判断是不是首位,首位不能减到0
            if (i != l){

                t_state -= getten(i);
                if ( DFS(t_state) == 0){
                    t_state+= temp*getten(i);
                    return 1;
                }
                t_state += temp*getten(i);
            }else
                t_state += (temp-1)*getten(i);

        }else{
            //如过该位是0
            int tt_state = t_state % getten(i-1);
            t_state /= getten(i+1);

            if ( DFS(t_state)== 0){
                t_state *= getten(i+1);
                t_state += tt_state;
                return 1;
            }
            t_state *= getten(i+1);
            t_state += tt_state;

        }
    }
    return sg[state] = 0;
}

int main(){

    fill(sg,sg+maxn,-1);
    sg[0] = 1;
    sg[1] = 0;
    for (int i = 2;i <= 999999;++i)
        sg[i] = DFS(i);
    //因为输入有前导0,所以要存字符串
    while( scanf("%s",str) != EOF ){
        //如果前导0,直接获胜
        if (*str == '0'){
            puts("Yes");
            continue;
        }
        int st;
        sscanf(str,"%d",&st);
        
        if ( sg[st] ) puts("Yes");
        else puts("No");
    }

    return 0;
}