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to Flatten Array in the C# Track

Published at May 03 2019 · 0 comments
Instructions
Test suite
Solution

Take a nested list and return a single flattened list with all values except nil/null.

The challenge is to write a function that accepts an arbitrarily-deep nested list-like structure and returns a flattened structure without any nil/null values.

For Example

input: [1,[2,3,null,4],[null],5]

output: [1,2,3,4,5]

Running the tests

To run the tests, run the command dotnet test from within the exercise directory.

Initially, only the first test will be enabled. This is to encourage you to solve the exercise one step at a time. Once you get the first test passing, remove the Skip property from the next test and work on getting that test passing. Once none of the tests are skipped and they are all passing, you can submit your solution using exercism submit FlattenArray.cs

Further information

For more detailed information about the C# track, including how to get help if you're having trouble, please visit the exercism.io C# language page.

Source

Interview Question https://reference.wolfram.com/language/ref/Flatten.html

FlattenArrayTest.cs

// This file was auto-generated based on version 1.2.0 of the canonical data.

using Xunit;

public class FlattenArrayTest
{
    [Fact]
    public void No_nesting()
    {
        var array = new object[]
        {
            0,
            1,
            2
        };
        var expected = new[] { 0, 1, 2 };
        Assert.Equal(expected, FlattenArray.Flatten(array));
    }

    [Fact(Skip = "Remove to run test")]
    public void Flattens_array_with_just_integers_present()
    {
        var array = new object[]
        {
            1,
            new object[] { 2, 3, 4, 5, 6, 7 },
            8
        };
        var expected = new[] { 1, 2, 3, 4, 5, 6, 7, 8 };
        Assert.Equal(expected, FlattenArray.Flatten(array));
    }

    [Fact(Skip = "Remove to run test")]
    public void Number_5_level_nesting()
    {
        var array = new object[]
        {
            0,
            2,
            new object[] { new object[] { 2, 3 }, 8, 100, 4, new object[] { new object[] { new object[] { 50 } } } },
            -2
        };
        var expected = new[] { 0, 2, 2, 3, 8, 100, 4, 50, -2 };
        Assert.Equal(expected, FlattenArray.Flatten(array));
    }

    [Fact(Skip = "Remove to run test")]
    public void Number_6_level_nesting()
    {
        var array = new object[]
        {
            1,
            new object[] { 2, new object[] { new object[] { 3 } }, new object[] { 4, new object[] { new object[] { 5 } } }, 6, 7 },
            8
        };
        var expected = new[] { 1, 2, 3, 4, 5, 6, 7, 8 };
        Assert.Equal(expected, FlattenArray.Flatten(array));
    }

    [Fact(Skip = "Remove to run test")]
    public void Number_6_level_nest_list_with_null_values()
    {
        var array = new object[]
        {
            0,
            2,
            new object[] { new object[] { 2, 3 }, 8, new object[] { new object[] { 100 } }, null, new object[] { new object[] { null } } },
            -2
        };
        var expected = new[] { 0, 2, 2, 3, 8, 100, -2 };
        Assert.Equal(expected, FlattenArray.Flatten(array));
    }

    [Fact(Skip = "Remove to run test")]
    public void All_values_in_nested_list_are_null()
    {
        var array = new object[]
        {
            null,
            new object[] { new object[] { new object[] { null } } },
            null,
            null,
            new object[] { new object[] { null, null }, null },
            null
        };
        Assert.Empty(FlattenArray.Flatten(array));
    }
}
using System.Collections;

public static class FlattenArray
{
    public static IEnumerable Flatten(IEnumerable input)
    {
        var list = new ArrayList();

        foreach (var obj in input)
        {
            if (obj == null)
            {
                continue;
            }

            if (obj is IEnumerable)
            {
                var inner = Flatten((IEnumerable)obj);
                foreach (var objInner in inner)
                {
                    list.Add(objInner);
                }
            }
            else
            {
                list.Add(obj);
            }
        }

        return list;
    }
}

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