CF Two Substrings-白红宇

CF Two Substrings

阅读量：6852 次

发布时间：2019-06-26

本文共 1530 字，大约阅读时间需要 5 分钟。

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 test(s)

input

ABA

output

NO

input

BACFAB

output

YES

input

AXBYBXA

output

NO 找到每组AB和BA的起点坐标，保存起来，然后用最远的一个BA的坐标减去最近的一个AB，或者最远的一个AB减去一个最近的BA,如果两者的差大于等于2，那么就YES.

#include 
         
          #include 
          
           #include 
           
            #include 
            
             #include 
             
              #include 
              #include 
               
                #include 
                
                 #include 
                 
                  #include 
                  
                   #include 
                   
                    #include 
                    
                     #include 
                     
                      using namespace std;int main(void){ char s[100005]; int ab[100005],ba[100005]; int p_ab = 0,p_ba = 0; scanf("%s",s); for(int i = 0;s[i];i ++) { if(s[i] == 'A' && s[i + 1] == 'B') { ab[p_ab] = i; p_ab ++; } else if(s[i] == 'B' && s[i + 1] == 'A') { ba[p_ba] = i; p_ba ++; } } if(!p_ab || !p_ba) { puts("NO"); return 0; } sort(ab,ab + p_ab); sort(ba,ba + p_ba); if(abs(ab[0] - ba[p_ba - 1]) >= 2 || abs(ba[0] - ab[p_ab - 1]) >= 2) puts("YES"); else puts("NO"); return 0;}