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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. int countAt(string &s)
  5. {
  6.     int amount = 0;
  7.  
  8.     for (char si : s)
  9.     {
  10.         if (si == '@')
  11.             amount++;
  12.         if (amount > 1)
  13.             return false;
  14.     }
  15.  
  16.     return amount == 1;
  17. }
  18.  
  19. bool checkLocal(string &local)
  20. {
  21.     for (char si : local)
  22.     {
  23.         if ('A' <= si && si <= 'Z')
  24.             continue;
  25.         if ('a' <= si && si <= 'z')
  26.             continue;
  27.         if ('0' <= si && si <= '9')
  28.             continue;
  29.         if (si == '.' || si == '_')
  30.             continue;
  31.         return false;
  32.     }
  33.     return true;
  34. }
  35.  
  36. bool checkDomain(string &domain)
  37. {
  38.     for (char si : domain)
  39.     {
  40.         if ('A' <= si && si <= 'Z')
  41.             continue;
  42.         if ('a' <= si && si <= 'z')
  43.             continue;
  44.         if (si == '.')
  45.             continue;
  46.         return false;
  47.     }
  48.  
  49.     int amount = 0;
  50.  
  51.     for (char si : domain)
  52.     {
  53.         if (si == '.')
  54.             amount++;
  55.     }
  56.  
  57.     if (amount == 0)
  58.         return false;
  59.  
  60.     for (int i = 0; i < domain.length() - 1; i++)
  61.     {
  62.         if (domain[i] == '.' && domain[i + 1] == '.')
  63.             return false;
  64.     }
  65.     return true;
  66. }
  67.  
  68. bool check(string &s)
  69. {
  70.     if (countAt(s) == false)
  71.         return false;
  72.  
  73.     string local = "";
  74.     string domain = "";
  75.  
  76.     int i = 0;
  77.     while (s[i] != '@')
  78.     {
  79.         local += s[i];
  80.         i++;
  81.     }
  82.  
  83.     i++;
  84.  
  85.     while (i < s.length())
  86.     {
  87.         domain += s[i];
  88.         i++;
  89.     }
  90.  
  91.     if (local.length() == 0 || domain.length() == 0)
  92.         return false;
  93.  
  94.     if (checkLocal(local) == false)
  95.         return false;
  96.  
  97.     if (checkDomain(domain) == false)
  98.         return false;
  99.     return true;
  100. }
  101.  
  102. int main()
  103. {
  104.     string s;
  105.     getline(cin, s);
  106.  
  107.     cout << (check(s) ? "VALID\n" : "INVALID\n");
  108.  
  109.     return 0;
  110. }
Success #stdin #stdout 0.01s 5284KB
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stdin
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Standard input is empty
stdout
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INVALID
https://ideone.com/0WLqVe
language:
C++ (gcc 8.3)
created:
6 hours ago
visibility:
public

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