B类-Codeforces Round #535 (Div. 3)C. Nice Garland

#include<iostream>
using namespace std;
string dir[6]={"RGB","RBG","BGR","BRG","GRB","GBR"};
int main(){
    int n;
    cin>>n;
    string s;
    cin>>s;
    int minn=100000000;
    int flag=0;
    //cout<<dir[5][1];
    for(int j=0;j<6;j++){
        int count=0;
        for(int i=0;i<n;i+=3){
            if(s[i]!=dir[j][0]) count++;
            if(i+1 >= n)
            break;
            else if(s[(i+1)]!=dir[j][1]) count++;
            if(i+2 >= n)
            break;
            else if(s[(i+2)]!=dir[j][2]) count++;
        }
        if(count<minn){
            minn=count;
            flag=j;
        }
    }
    cout<<minn<<endl;
    int i;
    for(i=0;i + 3 <n;i+=3){
        cout<<dir[flag];
    }
    int j = 0;
    for(i;i < n;i++)
    cout << dir[flag][j++];
    
    //if(n%3==)
    return 0;
}
//比赛结束了几分钟才改好，emmmmmmm，笨死啦。