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  1. #include <iostream>
  2. #include <vector>
  3. using namespace std;
  4.  
  5. int main() {
  6.     string s;
  7.     cin >> s;
  8.     int n = s.length();
  9.     //дублируем строку, чтобы иметь возможность просмотреть все циклические перестановки
  10.     s += s;
  11.     const int p = 31;
  12.     vector <long long> p_pow (2*n); //вектор степеней числа p
  13.     p_pow[0] = 1;
  14.     for (int i = 1; i < 2*n; ++i) p_pow[i] = p * p_pow[i-1];
  15.     long long P1 = 0, P2 = 0;
  16.     for (int i = 0; i < n; ++i) {
  17.         P1 += (s[i] - 'a' + 1) * p_pow[i];
  18.         P2 += (s[n - i - 1] - 'a' + 1) * p_pow[i];
  19.     }
  20.     if (P1 == P2) {
  21.         bool check = true;
  22.         for (int i = 0; i < n; ++i)
  23.             if (s[i] != s[n - i - 1]) check = false;
  24.         if (check) {
  25.             cout << "yes";
  26.             return 0;
  27.         }
  28.     }
  29.     for (int i = 0; i < n; ++i) {
  30.         P1 += (s[i+n] - 'a' + 1)*p_pow[i+n] - (s[i] - 'a' + 1)*p_pow[i];
  31.         P2 = (P2 - (s[i] - 'a' + 1)*p_pow[n + i - 1]) * p_pow[2] + (s[i+n]-'a' + 1) * p_pow[i+1];
  32.         if (P1 == P2) {
  33.             bool check = true;
  34.             for (int j = i + 1; j < i + 1 + n; ++j)
  35.                 if (s[j] != s[2*i + 1 + n - j]) check = false;
  36.             if (check) {
  37.                 cout << "yes";
  38.                 return 0;
  39.             }
  40.         }
  41.     }
  42.     cout << "no";
  43.     return 0;
  44. }
  45.  
Success #stdin #stdout 0s 5584KB
comments (?)
stdin
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array
stdout
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yes
https://ideone.com/TB7wcp
problem B. Hash
language:
C++14 (gcc 8.3)
created:
3 years ago
visibility:
secret

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