title: How can you remove duplicate characters in a string?
body: <p>I have to implements a function that takes a string as an input and finds the non-duplicate character from this string.</p>
  
  <p>So an an example is if I pass string str = "DHCD" it will return "DHC"
  or str2 = "KLKLHHMO" it will return "KLHMO"</p>