// Remove duplicates from a linked list.

#define CATCH_CONFIG_MAIN
#include <catch.hpp>

#include <unordered_set>

#include "libcc2x.cc"

IntItem* remove_duplicates(IntItem* head) {
  std::unordered_set<int> seen;

  // TODO(michaelh): is [&] or [&seen] better style?
  return filter(head, [&](int v) {
    if (seen.find(v) != seen.end()) {
      return true;
    }
    seen.emplace(v);
    return false;
  });
}

TEST_CASE("cc21", "remove_duplicates") {
  auto first = make_list({2, 3, 4});
  CHECK(to_string(first) == " 1 2 3 4");
  first = filter(first, [](int v) { return v % 2 == 0; });
  CHECK(to_string(first) == " 1 3");

  first->tail()->emplace(7)->emplace(8);
  CHECK(to_string(first) == " 1 3 7 8");

  first->tail()->emplace(3)->emplace(7);
  CHECK(to_string(first) == " 1 3 7 8 3 7");
  first = remove_duplicates(first);
  CHECK(to_string(first) == " 1 3 7 8");
}