Codeforces Round #306 (Div. 2) A. Two Substrings 水题

A. Two Substrings

Time Limit: 20 Sec

Memory Limit: 256 MB

题目连接

http://codeforces.com/contest/550/problem/A

Description

You are given string s. Your task is to determine if the given string s contains two non-overlapping substrings "AB" and "BA" (the substrings can go in any order).

Input

The only line of input contains a string s of length between 1 and 105 consisting of uppercase Latin letters.

Output

Print "YES" (without the quotes), if string s contains two non-overlapping substrings "AB" and "BA", and "NO" otherwise.

Sample Input

ABA

Sample Output

NO

HINT

题意

判断字符串是否存在不重合的AB和BA

题解：

虽然是一道傻逼题，但是被cha的人很多

我提供两组数据ABACCAB 和ABAB

这两组数据，来感受一下～

代码：

//qscqesze
#include <cstdio>
#include <cmath>
#include <cstring>
#include <ctime>
#include <iostream>
#include <algorithm>
#include <set>
#include <vector>
#include <sstream>
#include <queue>
#include <typeinfo>
#include <fstream>
#include <map>
#include <stack>
typedef long long ll;
using namespace std;
//freopen("D.in","r",stdin);
//freopen("D.out","w",stdout);
#define sspeed ios_base::sync_with_stdio(0);cin.tie(0)
#define test freopen("test.txt","r",stdin)
#define maxn 2000001
#define mod 10007
#define eps 1e-9
int Num;
char CH[];
const int inf=0x3f3f3f3f;
const ll infll = 0x3f3f3f3f3f3f3f3fLL;
inline ll read()
{
    ll x=,f=;char ch=getchar();
    while(ch<''||ch>''){if(ch=='-')f=-;ch=getchar();}
    while(ch>=''&&ch<=''){x=x*+ch-'';ch=getchar();}
    return x*f;
}
inline void P(int x)
{
    Num=;if(!x){putchar('');puts("");return;}
    while(x>)CH[++Num]=x%,x/=;
    while(Num)putchar(CH[Num--]+);
    puts("");
}
//**************************************************************************************
 
int main()
{
    //test;
    string s;
    string s1;
    cin>>s;
    s1=s;
    int flag=;
    int n=s.size();
    for(int i=;i<n-;i++)
    {
        if(s1[i]=='B'&&s1[i+]=='A')
        {
            flag=,s1[i]='#',s1[i+]='#';
            break;
        }
    }
    if(flag==)
    {
        for(int i=;i<n-;i++)
        {
            if(s1[i]=='A'&&s1[i+]=='B')
            {
                cout<<"YES"<<endl;
                return ;
            }
        }
    }
    s1=s;
    flag=;
    for(int i=;i<n-;i++)
    {
        if(s1[i]=='A'&&s1[i+]=='B')
        {
            flag=,s1[i]='#',s1[i+]='#';
            break;
        }
    }
    if(flag==)
    {
        for(int i=;i<n-;i++)
        {
            if(s1[i]=='B'&&s1[i+]=='A')
            {
                cout<<"YES"<<endl;
                return ;
            }
        }
    }
    cout<<"NO"<<endl;
    return ;
}