Finding duplicate elements

[vino via Digitalmars-d-learn]

Hi All,

 Request your help in finding duplicate element without sorting 
as per the below example

```
Example:
string[] args = [" test3", "test2 ", " test1 ", " test1 ", " "];

Output Required:
If duplicate element found then print "Duplicate element found: 
<element name>"
else print ["test3", "test2", "test1"];
```
From,
Vino.B