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

题目传送门

 /*
     水题：遍历一边先找AB，再BA，再遍历一边先找BA，再AB，两种情况满足一种就YES
 */
 #include <cstdio>
 #include <iostream>
 #include <cstring>
 #include <cmath>
 #include <algorithm>
 #include <vector>
 #include <map>
 #include <queue>
 #include <set>
 #include <string>
 #include <stack>
 using namespace std;

 typedef long long ll;
 const int MAXN = 1e5 + ;
 const int INF = 0x3f3f3f3f;
 char s[MAXN];

 int main(void)        //Codeforces Round #306 (Div. 2) A. Two Substrings
 {
     while (scanf ("%s", s) == )
     {
         bool ok1 = false, ok2 = false, ok3 = false, ok4 = false;
         int len = strlen (s);    int p = ;
         for (int i=; i<len; ++i)
         {
             if (i < len -  && !ok1 && s[i] == 'A' && s[i+] == 'B')
             {
                 ok1 = true;    i++;
             }
             else if (i < len -  && ok1 && s[i] == 'B' && s[i+] == 'A')
             {
                 ok2 = true;    break;
             }
         }
         for (int i=; i<len; ++i)
         {
             if (i < len -  && !ok3 && s[i] == 'B' && s[i+] == 'A')
             {
                 ok3 = true;    i++;
             }
             else if (i < len -  && ok3 && s[i] == 'A' && s[i+] == 'B')
             {
                 ok4 = true;    break;
             }
         }

         if ((ok1 && ok2) || (ok3 && ok4))    puts ("YES");
         else    puts ("NO");
     }

     return ;
 }

 /*
 ABA
 BACFAB
 AXBYBXA
 */