P2562kitty cat gene

This question is NOI Anhui province topics, but the difficulty is not so difficult.

This question is a string of recursive problem, there are a lot of chiefs with tree line to write (I also want to learn the tree line, lowbit blow). Title means all the same the output B or A, different from the divided two sub-strings of the same length, and outputs C. I see this will be very easy to think of recursive plus two points, but how to write the above function it? I suddenly wanted to retreat, and then come strategy: enumeration substring, if there are different recursively binary output C, until the same outputs A, B.

1. Avoid low error, eg.string s [], (mid + 1, left) ,, would delay a lot of time to debug

2. The skilled use of recursive half

Code

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
#define N 100001
using namespace std;
string s;//!
bool flag;
void work(int left,int right){
    flag=true;
    int mid=(left+right)/2;
    for(int i=left+1;i<=right;i++){
        if(s[i]!=s[i-1]){
            flag=false;
            break;
        }
    }
    if(flag==false){
        cout<<"C";
        work(left,mid);
        work(mid+1,right);//!
        return;
    }    
    if(flag==true){
        if(s[left]=='0') cout<<"A";
        else if(s[left]=='1') cout<<"B";
    }
    return;
}
int main(){
    cin>>s;
    int len=s.length();
    work(0,len-1);//!
    return 0;
}