project-euler

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Euler_55.cpp (863B)

      1 #include <sstream>
      2 
      3 #include "Euler.h"
      4 
      5 bool isPalindrome(cpp_int i)
      6 {
      7     std::ostringstream oss;
      8     oss << i;
      9 
     10     std::string temp = oss.str();
     11 
     12     for (unsigned int j = 0; j < temp.length() / 2 + 1; ++j)
     13         if (temp.at(j) != temp.at(temp.length() - 1 - j))
     14             return false;
     15 
     16     return true;
     17 }
     18 
     19 cpp_int reverse(cpp_int i)
     20 {
     21     cpp_int reverse = 0;
     22 
     23     while(i > 0)
     24     {
     25         reverse = reverse * 10 + (i % 10);
     26         i /= 10;
     27     }
     28 
     29     return reverse;
     30 }
     31 
     32 cpp_int Euler::LychrelNumbers()
     33 {
     34     int lychel = 9999;
     35 
     36     for (int i = 1; i < 10000; ++i)
     37     {
     38         cpp_int current(i);
     39 
     40         for (int j = 0; j < 50; ++j)
     41         {
     42             current = current + reverse(current);
     43 
     44             if (isPalindrome(current))
     45             {
     46                 --lychel;
     47                 break;
     48             }
     49         }
     50     }
     51 
     52     return lychel;
     53 }