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

 1 /*
 2     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
 3 */
 4 #include <cstdio>
 5 #include <iostream>
 6 #include <cstring>
 7 #include <cmath>
 8 #include <algorithm>
 9 #include <vector>
10 #include <map>
11 #include <queue>
12 #include <set>
13 #include <string>
14 #include <stack>
15 using namespace std;
16 
17 typedef long long ll;
18 const int MAXN = 1e5 + 10;
19 const int INF = 0x3f3f3f3f;
20 char s[MAXN];
21 
22 int main(void)        //Codeforces Round #306 (Div. 2) A. Two Substrings
23 {
24     while (scanf ("%s", s) == 1)
25     {
26         bool ok1 = false, ok2 = false, ok3 = false, ok4 = false;
27         int len = strlen (s);    int p = 0;
28         for (int i=0; i<len; ++i)
29         {
30             if (i < len - 1 && !ok1 && s[i] == 'A' && s[i+1] == 'B')
31             {
32                 ok1 = true;    i++;
33             }
34             else if (i < len - 1 && ok1 && s[i] == 'B' && s[i+1] == 'A')
35             {
36                 ok2 = true;    break;
37             }
38         }
39         for (int i=0; i<len; ++i)
40         {
41             if (i < len - 1 && !ok3 && s[i] == 'B' && s[i+1] == 'A')
42             {
43                 ok3 = true;    i++;
44             }
45             else if (i < len - 1 && ok3 && s[i] == 'A' && s[i+1] == 'B')
46             {
47                 ok4 = true;    break;
48             }
49         }
50 
51         if ((ok1 && ok2) || (ok3 && ok4))    puts ("YES");
52         else    puts ("NO");
53     }
54 
55 
56     return 0;
57 }
58 
59 /*
60 ABA
61 BACFAB
62 AXBYBXA
63 */
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