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  1. #include <cstring>
  2. #include <cctype>
  3. #include <iostream>
  4.  
  5. bool YPalindrome(const char* candidate)
  6. {
  7.     const char* left = candidate;
  8.     const char* right = candidate + std::strlen(candidate) - 1;
  9.  
  10.     while (left <= right)
  11.     {
  12.         bool leftAlpha = std::isalpha(*left);
  13.         bool rightAlpha = std::isalpha(*right);
  14.  
  15.         if (leftAlpha && rightAlpha) // only compare alphabetic characters.
  16.         {
  17.             if (std::tolower(*left) != std::tolower(*right))
  18.                 return false;
  19.  
  20.             ++left, --right;
  21.         }
  22.         else
  23.         {
  24.             if (!leftAlpha) // skip non-alphabetic characters.
  25.                 ++left;
  26.  
  27.             if (!rightAlpha)
  28.                 --right;
  29.         }
  30.     }
  31.  
  32.     return true;
  33. }
  34.  
  35. void reportIfPalindrome(const char* s)
  36. {
  37.     std::cout << '"' << s << "\" ";
  38.  
  39.     if (YPalindrome(s))
  40.         std::cout << "is a palindrome.\n";
  41.     else
  42.         std::cout << "is not a palindrome.\n";
  43. }
  44.  
  45. int main()
  46. {
  47.     const unsigned phrases = 4;
  48.     const char* str [phrases] =
  49.     {
  50.         "Madam, I'm Adam.",
  51.         "Ra cecar",
  52.         "not a palindrome",
  53.         "A man, a plan, a canal - Panama!"
  54.     };
  55.  
  56.     for (unsigned i = 0; i < phrases; ++i)
  57.         reportIfPalindrome(str[i]);
  58. }
Success #stdin #stdout 0s 3340KB
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stdin
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Standard input is empty
stdout
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"Madam, I'm Adam." is a palindrome.
"Ra cecar" is a palindrome.
"not a palindrome" is not a palindrome.
"A man, a plan, a canal - Panama!" is a palindrome.
https://ideone.com/rdjP1c
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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