Szathmáry László honlapja @ DEIK | Nim2 / remove duplicates

Let's solve this exercise:

"Consider the following list: [5, 2, 3, 5, 1, 4, -200, 5, 1, 3, 2, 2, 5] . Remove the duplicates, i.e. an element should be present in the list maximum once. Let the result be a sorted list."

Solution 1 (arbitrary order)

If we need to remove the duplicates, then we can immediately think of using a set.

import std/sequtils # toSeq(iter), map, filter
import std/algorithm # sorted(seq), reversed(seq)
import std/sets

let
li = @[5, 2, 3, 5, 1, 4, -200, 5, 1, 3, 2, 2, 5]
result = sorted(li.toHashSet.toSeq)

echo result # @[-200, 1, 2, 3, 4, 5]

Solution 2 (keep order)

If we have a seq and we want to remove the duplicates, then there's a seq method for this (link):

func deduplicate[T](s: openArray[T]; isSorted: bool = false): seq[T]

It removes the duplicates AND keeps the original order of the elements.

In this case, it's not necessary to convert the seq to a set and then back to a seq.

import std/sequtils # toSeq(iter), map, filter
import std/algorithm # sorted(seq), reversed(seq)

let
li = @[5, 2, 3, 5, 1, 4, -200, 5, 1, 3, 2, 2, 5]

echo li.deduplicate() # @[5, 2, 3, 1, 4, -200] ; the order is kept

echo sorted(li.deduplicate) # @[-200, 1, 2, 3, 4, 5]