「日常训练」Divisibility by Eight（Codeforces Round 306 Div.2 C）

Posted 2021-01-10 samhx

题意与分析

极简单的数论+思维题。

代码

#include <bits/stdc++.h>
#define MP make_pair
#define PB emplace_back
#define fi first
#define se second
#define ZERO(x) memset((x), 0, sizeof(x))
#define ALL(x) (x).begin(),(x).end()
#define rep(i, a, b) for (repType i = (a); i <= (b); ++i)
#define per(i, a, b) for (repType i = (a); i >= (b); --i)
#define QUICKIO                      ios::sync_with_stdio(false);     cin.tie(0);                      cout.tie(0);
using namespace std;
using ll=long long;
using repType=int;

bool judge(int x)
{
    if(x%8==0)
    {
        cout<<"YES"<<endl<<x<<endl;
        return true;
    }
    return false;
}

bool judge(int x,int y)
{
    if(judge(x) || judge(y) || judge(x*10+y)) return true;
    return false;
}

int main()
{
    string str; cin>>str;
    if(str.length()<=2)
    {
        if(str.length()==1)
        {
            if((str[0]-‘0‘)%8) cout<<"NO"<<endl;
            else
            {
                cout<<"YES"<<endl<<str<<endl;
            }
            return 0;
        }
        else
        {
            if((str[0]-‘0‘)%8==0)
            {
                cout<<"YES"<<endl<<str[0]<<endl;
                return 0;
            }
            else if((str[1]-‘0‘)%8==0)
            {
                cout<<"YES"<<endl<<str[1]<<endl;
                return 0;
            }
            else if(((str[1]-‘0‘)*10+str[0]-‘0‘)%8==0)
            {
                cout<<"YES"<<endl<<str<<endl;
                return 0;
            }
            cout<<"NO"<<endl;
            return 0;
        }
    }
    rep(i,0,str.length()-3)
    {
        int x=str[i]-‘0‘; 
        if(judge(x)) return 0;
        rep(j,i+1,str.length()-2)
        {
            int y=str[j]-‘0‘;
            if(judge(y) || judge(x,y)) return 0;
            rep(k,j+1,str.length()-1)
            {
                int z=str[k]-‘0‘;
                if(judge(z) || judge(x,z) || judge(y,z)) return 0;
                if(z%2) continue;
                //cout<<x<<" "<<y<<" "<<z<<endl;
                //cout<<(!(x%2))<<" "<<(y*10+z)%8<<((!(x%2)) && (y*10+z)%8==4)<<endl;
                if((!(x%2) && (y*10+z)%8==0) || (x%2 && (y*10+z)%8==4))
                {
                    cout<<"YES"<<endl;
                    //cout<<i<<" "<<j<<" "<<k<<endl;
                    rep(p,0,str.length()-1)
                    {
                        //cout<<"("<<p<<") ";
                        if(p<i || p==i || p==j || p==k) cout<<str[p];
                    }
                    cout<<endl;
                    return 0;
                }
            }
        }
    }
    cout<<"NO"<<endl;
    return 0;
}