How to remove duplicated elements from vector? [duplicate]

Question

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How to remove duplicates from unsorted std::vector while keeping the original ordering using algorithms? (8 answers)

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Hence I have std::vector<type>.

Class type has no operator< but has operator==. Thus, I cannot sort my vector using std::unique.

How I can remove duplicated elements from vector?

Answer 1

I think best option is to write some binary predicate to use for the sorting of the vector and use std::unique afterwards. Keep in mind that the predicate must be transitive!

If this is not an option you can not do anything else but use the quardatic algorithm:

std::vector<type> a
std::vector<type> result;
for (unsigned i = 0; i < a.size(); ++i) {
  bool repeated = false;
  for (int j = 0; j < i; ++j) {
    if (a[j] == a[i]) {
      repeated = true;
      break;
    }
  }
  if (!repeated) {
    result.push_back(a[i]);
  }
}

// result stores the unique elements.