Problem with initializing an array of List<int> with Initialize method

Question

I want to implement a graph with an array of List<int>, but when I try to initialize the entries with Array.Initialize() with the default values (by calling a parameterless constructor of List<int>), it's like the method was never called and after that all entries are still null!

int n = int.Parse(Console.ReadLine()); // number of nodes 
List<int>[] g = new List<int>[n]; //graph
g.Initialize();

It's fine when I iterate over the collection and intitialize, but why is there a problem with the method Initialize()?

List<T>[] is an array though, and that's what he wrote in his code. Could you explain further what exactly you're talking about? — Blindy
– Blindy, Commented Jan 5, 2021 at 17:31
@Blindy Your right, I am blind, that is in fact an array of List<int>. — asawyer
– asawyer, Commented Jan 5, 2021 at 17:32

Blindy · Accepted Answer · 2021-01-05 17:30:42Z

1

Don't use Array.Initialize, ever. Read the documentation on the function, it has an entire page of warnings, including a huge red caution box.

Instead initialize your array as you would any other:

for(int i = 0; i < g.Count; ++i)
    g[i] = new();

answered Jan 5, 2021 at 17:30

Blindy

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Navid Golforoushan · Accepted Answer · 2021-01-05 17:36:08Z

0

You should change your data-type to int[]=>

var myArray = new int[n];

Or If you need for any reason List you can initializing it as shown in below section=>

var defaultValue=65;
var myListWithDefaultValue = Enumerable.Repeat(defaultValue, n).ToList();

answered Jan 5, 2021 at 17:36

Navid Golforoushan

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