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  1. #include <iterator>
  2. #include <iostream>
  3.  
  4. template <typename In, typename Out>
  5.    Out t9_transform(In f, In l, Out out)
  6. {
  7.     auto magic = [](decltype(*f) i) { return '2' + std::min(7, (i - (i >> 4)) / 3); };
  8.     decltype(0+*f) previous = 0;
  9.  
  10.     for(;f!=l;++f) {
  11.         if (*f>='a' && *f<='z') {
  12.             auto idx = *f - 'a';
  13.  
  14.             auto digit = magic(idx);
  15.             if (digit == previous) *out++ = ' ';
  16.             previous = digit;
  17.  
  18.             static_assert(std::is_signed<decltype(idx)>::value, "difference type is required to be signed here");
  19.             for (; idx>=0 && digit == magic(idx); --idx)
  20.                 *out++ = digit;
  21.         } else
  22.             *out++ = '0';
  23.     }
  24.  
  25.     return out;
  26. }
  27.  
  28. std::string t9(std::string const& input)
  29. {
  30.     std::string result;
  31.     // result.reserve(2*input.size());
  32.     t9_transform(begin(input), end(input), std::back_inserter(result));
  33.     return result;
  34. }
  35.  
  36. int main()
  37. {
  38.     const std::string input = "abcdefghijklmnopqrstuvwxyz";
  39.     auto output = t9_transform(begin(input), end(input), std::ostream_iterator<char>(std::cout));
  40.  
  41.     std::cout << std::endl << t9("hello world!") << std::endl;
  42.  
  43.     // or, how about translating all of stdin to stdout, in streaming mode?
  44.     *t9_transform(std::istreambuf_iterator<char>(std::cin), std::istreambuf_iterator<char>(), output) = '\n';
  45. }
  46.  
Success #stdin #stdout 0s 2992KB
comments (?)
stdin
copy 
some poetry wouldn't be remiss
stdout
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2 22 2223 33 3334 44 4445 55 5556 66 6667 77 777 77778 88 8889 99 999 9999
4433555 5556660966677755530
7777666 633076663387779990 966688555366080223307773364447777 7777
https://ideone.com/O5sLIS
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
secret

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