Removing duplicate characters from string using STL

Question

Is there a way to remove duplicate characters from a string like they can be removed from vectors as below

sort( vec.begin(), vec.end() );
vec.erase( unique( vec.begin(), vec.end() ), vec.end() );

or do I just have to code up a basic solution for it? What I have thought:

I could add all the characters into a set

That depends on what you mean by "duplicate" characters. Does a string "ABACADAF" have duplicate As? Or would you just want "AABACAD" to remove the first A in the double AA? — Zac Howland
– Zac Howland, Commented Jan 14, 2014 at 18:42
Why would you go for an O(n log(n)) solution while you can do it in O(n) as explained here in the Second method? — adrin
– adrin, Commented Jan 14, 2014 at 18:44
Thanks turns out i was missing out the "str" part from str.erase(...) and was ending up with an error thinking this cant be done.. my bad.. — otaku
– otaku, Commented Jan 14, 2014 at 19:04

Konrad Rudolph · Accepted Answer · 2014-01-14 18:47:27Z

14

The whole point of C++’ algorithm and container design is that the algorithms are – as far as possible – container agnostic.

So the same algorithm that works on vectors works – of course! – on strings.

std::sort(str.begin(), str.end());
str.erase(std::unique(str.begin(), str.end()), str.end());

The same even works on old-style C strings – with the small difference that you cannot erase their tails, you need to manually truncate them by re-setting the null terminating character (and there are no begin and end member functions so you’d use pointers to the first and one-past-last character).

answered Jan 14, 2014 at 18:47

Konrad Rudolph

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