Remove duplicate dart-CodePudding

there is a list:

@Koolkid3
@Peetea
@Peetea
@Ruptan
@bulunabu
@ptygma
@ptygma

Here's what to get:

@Koolkid3
@Ruptan
@bulunabu

If there are duplicates, then you need to remove them completely. Therefore, toSet() will not work here. How to do it?

CodePudding user response：

You can convert List to Set to remove duplicates. If needed again convert it into list.

 List<String> list = ["a", "v", "a"];

 print(list.toSet().toList()); //[a, v]

Removing duplicates and itself

List<String> list = ["a", "v", "a"];

list.removeWhere(
  (String s1) => list.where((s2) => s1 == s2).length > 1,
);

print(list); /// [v]

CodePudding user response：

What about the following:

  List<String> list = [
    "@Koolkid3",
    "@Peetea",
    "@Peetea",
    "@Ruptan",
    "@bulunabu",
    "@ptygma",
    "@ptygma"
  ];
  var occurrenceCount = Map();

  list.forEach((x) => occurrenceCount[x] = !occurrenceCount.containsKey(x) ? (1) : (occurrenceCount[x]   1));

  list.retainWhere((element) => occurrenceCount[element] == 1);
  print(list);

Use a Map to count occurrence of each item, then use retainWhere to only keep the items that occur once.