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  1. #include <string>
  2. #include <cstdlib>
  3.  
  4. long firstDigitToEnd(long n) {
  5.     bool neg = (n < 0);                  // Preserve signed-ness.
  6.     if (neg) { n = labs(n); }            // Obtain absolute value, for convenience.
  7.  
  8.     std::string num = std::to_string(n); // Convert number to string.
  9.  
  10.     char first = num[0];                 // Obtain first digit.
  11.     num.erase(0, 1);                     // Erase first digit, shift rest forwards.
  12.     num.push_back(first);                // Append first digit to end.
  13.  
  14.     // And we're done.  Convert string back to number, restore signed-ness.
  15.     return (neg ? -(std::stol(num)) : std::stol(num));
  16. }
  17.  
  18. // -----
  19.  
  20. // Testing code.
  21.  
  22. #include <iostream>
  23. #include <limits>
  24.  
  25. void readCin(long& l);
  26.  
  27. int main() {
  28.     long n = 0;
  29.  
  30.     do {
  31.         if (n) {
  32.             std::cout << "Result: " << firstDigitToEnd(n) << std::endl;
  33.         }
  34.  
  35.         std::cout << "Input number, or 0 to exit: ";
  36.         readCin(n);
  37.     } while (n);
  38.  
  39.     std::cout << "...And we're gone." << std::endl;
  40. }
  41.  
  42. // Read a number, or clear the buffer if non-number is entered.
  43. void readCin(long& l) {
  44.     using std::cin;
  45.  
  46.     cin >> l;
  47.     cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
  48.  
  49.     if (cin.fail()) {
  50.         cin.clear();
  51.         cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
  52.         l = 0;
  53.     }
  54. }
Success #stdin #stdout 0s 3476KB
comments (?)
stdin
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123456789
-123456789
999999998
-999999998
0
stdout
copy 
Input number, or 0 to exit: Result: 234567891
Input number, or 0 to exit: Result: -234567891
Input number, or 0 to exit: Result: 999999989
Input number, or 0 to exit: Result: -999999989
Input number, or 0 to exit: ...And we're gone.
https://ideone.com/8oWH2o
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
secret

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