Add leading zero's to string, without (s)printf

Question

I want to add a variable of leading zero\'s to a string. I couldn\'t find anything on Google, without someone mentioning (s)printf, but I want to do this without (s)printf.<

Answer 1

I can give this one-line solution if you want a field of n_zero zeros:

  std::string new_string = std::string(n_zero - old_string.length(), '0') + old_string;

For example: old_string = "45"; n_zero = 4; new_string = "0045";