Not if you use a hash set. This is expected O(n) time to de-duplicate an array of integers while maintaining the original order (more explicitly written than I normally would in Rust for didactical purposes):

    let mut hash_set = HashSet::new();
    let mut len = 0;

    for i in 0..arr.len() {
        if !hash_set.contains(&arr[i]) {
            hash_set.insert(arr[i]);
            arr[len] = arr[i];
            len += 1;
        }
    }

    arr.truncate(len);

But to order a list is O(n log n)