hihocoder #1061 : Beautiful String

#include<fstream>
#include<iostream>
#include<string>
#include<math.h>
using namespace std;
#define FOR(i,b,e) for(int i=(b);i<=(e);i++)
#define FORE(i,b,e) for(int i=(b);i>=(e);i--)
#define maxnum 503
int step,last,pres;
int main()
{
#ifdef DEBUG_
ifstream fin("G:/1.txt");
#define cin fin
#endif
int M,N;
string str;
cin>>N;

FOR(i,1,N){
cin>>M;
cin>>str;
if(M<3){
cout<<"NO"<<endl;
continue;
}
step=0;last=0;pres=0;
char a=0;
int flag=0;
FOR(i,0,M-1){
if(a+1==str[i]){

step=(step==2?2:step+1);
last=pres;
pres=1;
a=str[i];
if(step==2&&last==1){
flag=1;
break;
}

}else if(a==str[i]){
pres++;
if(step==1){
if(pres>last)
step=0;
}else if(step==2){
if(pres==last){
flag=1;
break;
}
}
}else{
step=0;
last=0;
pres=1;
a=str[i];
}
}
if(flag)
cout<<"YES"<<endl;
else
cout<<"NO"<<endl;
}
cout<<endl;
return 0;
}