title: How to sort filenames with possibly unpadded numbers in c++?
body: <p>I need to sort filenames that can have a common root, but are then followed by numbers that are not necessarily padded uniformely; one example is what you obtain when you rename multiple files in Windows.</p>
  
  <p>filenamea (1).txt
  filenamea (2).txt
  ...
  filenamea (10).txt
  ...
  filenamea (100).txt
  ...
  filenameb.txt
  ...
  filenamec (1).txt
  filenamec (2).txt</p>
  
  <p>and so on...</p>