update

Task/Remove-duplicate-elements/C++/remove-duplicate-elements-5.cpp

@@ -0,0 +1,14 @@
+#include <algorithm>
+#include <iostream>
+#include <vector>
+
+int main() {
+  std::vector<int> data = {1, 2, 3, 2, 3, 4};
+
+  std::sort(data.begin(), data.end());
+  data.erase(std::unique(data.begin(), data.end()), data.end());
+
+  for(int& i: data) std::cout << i << " ";
+  std::cout << std::endl;
+  return 0;
+}

Task/Remove-duplicate-elements/C/remove-duplicate-elements-3.c

@@ -3,7 +3,7 @@
 
 int icmp(const void *a, const void *b)
 {
-#define _I(x) *(int*)x
+#define _I(x) *(const int*)x
 	return _I(a) < _I(b) ? -1 : _I(a) > _I(b);
 #undef _I
 }

Task/Remove-duplicate-elements/Erlang/remove-duplicate-elements.erl

@@ -1,2 +1,4 @@
 List = [1, 2, 3, 2, 2, 4, 5, 5, 4, 6, 6, 5].
 UniqueList = gb_sets:to_list(gb_sets:from_list(List)).
+% Alternatively the builtin:
+Unique_list = lists:usort( List ).

Task/Remove-duplicate-elements/Racket/remove-duplicate-elements-1.rkt

@@ -0,0 +1,2 @@
+-> (remove-duplicates '(2 1 3 2.0 a 4 5 b 4 3 a 7 1 3 x 2))
+'(2 1 3 2.0 a 4 5 b 7 x)

Task/Remove-duplicate-elements/Racket/remove-duplicate-elements-2.rkt

@@ -0,0 +1,2 @@
+(define (unique/hash lst)
+  (hash-keys (for/hash ([x (in-list lst)]) (values x #t))))

Task/Remove-duplicate-elements/Racket/remove-duplicate-elements-3.rkt

@@ -0,0 +1 @@
+(define unique/set (compose1 set->list list->set))

Task/Remove-duplicate-elements/Racket/remove-duplicate-elements-4.rkt

@@ -0,0 +1,4 @@
+(define (unique seq #:same-test [same? equal?])
+  (for/fold ([res '()])
+            ([x seq] #:unless (memf (curry same? x) res))
+    (cons x res)))