Create Multiple Lists from String using Different Splits

Question

This is example code.

I have string with the names of planets, their order, and color, separated by spaces and NewLines.

I do not want to modify the string to change the results.

I want to create 3 Lists, Order, Name and Color from the string.

| Order      | Name       | Color      |
|------------|------------|------------|
| First      | Mercury    | Gray       |
| Second     | Venus      | Yellow     |
| Third      | Earth      | Blue       |
| Fourth     | Mars       | Red        |

This will create a List from the string, split by NewLine.

string planets = "First Mercury Gray" 
                + Environment.NewLine 
                + "Second Venus Yellow"
                + Environment.NewLine
                + "Third Earth Blue"
                + Environment.NewLine 
                + "Fourth Mars Red"
                + Environment.NewLine;


List<string> PlanetOrder = planets.Split(
               new[] { Environment.NewLine }, StringSplitOptions.None).ToList();   

List<string> PlanetName = planets.Split(
               new[] { Environment.NewLine }, StringSplitOptions.None).ToList();

List<string> PlanetColor = planets.Split(
               new[] { Environment.NewLine }, StringSplitOptions.None).ToList();

But within each line how can I also Split by space and choose word [1]Order, [2]Name, [3]Color?

planets.Split(' ')[2]; //Name

Ben · Accepted Answer · 2017-08-03 05:44:42Z

6

You can do the following. First split the string by Environment.NewLine, then split each line of the result by space and add the items to the different lists.

string planets = "First Mercury Gray"
            + Environment.NewLine
            + "Second Venus Yellow"
            + Environment.NewLine
            + "Third Earth Blue"
            + Environment.NewLine
            + "Fourth Mars Red"
            + Environment.NewLine;

List<string> PlanetOrder = new List<string>();
List<string> PlanetName = new List<string>();
List<string> PlanetColor = new List<string>();
string[] lines = planets.Split(new string[] {Environment.NewLine}, StringSplitOptions.RemoveEmptyEntries);
foreach (string line in lines)
{
    string[] arr = line.Split(' ');
    PlanetOrder.Add(arr[0]);
    PlanetName.Add(arr[1]);
    PlanetColor.Add(arr[2]);
}

answered Aug 3, 2017 at 5:44

Ben

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6 Comments

Matt McManis Over a year ago

Thanks, I am trying it in my project. I will get back to you.

Matt McManis Over a year ago

Your solution worked. I am comparing with Xavave's answer for speed because in my real program I apply this solution to a very long list with many splits.

Ben Over a year ago

That's ok :), but i recommend to make a test with a long list with both solutions. I disagree with Xavaeve's answer about the performance.

Ben Over a year ago

Nothing is wrong, but he is splitting every string three times, but necessary is only one time and I think that converting the splitted lines to List is slower than using the string array. I did a test of both alogrithms and had a different result than him about the performance. See for yourself and test both algorithms and let us know what your result is

Matt McManis Over a year ago

I tested both solutions with the real list on rextester. I looked at the absolute running time and cpu time. Both performed within milliseconds of each other. Each sometimes slower, sometimes faster. His performs just as fast, maybe it has to do with the compiler. I will use yours so to not split more than necessary.

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Andrés Robinet · Accepted Answer · 2017-08-03 05:56:25Z

2

A LINQ approach:

public enum PlanetColumn
{
    Order = 0,
    Name = 1,
    Color = 2
}

string planets = "First Mercury Gray" 
            + Environment.NewLine 
            + "Second Venus Yellow"
            + Environment.NewLine
            + "Third Earth Blue"
            + Environment.NewLine 
            + "Fourth Mars Red"
            + Environment.NewLine;

var lookup = planets
    .Split(new[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries)
    .SelectMany(p => p.Trim().Split(' ').Select((value, colIndex) => new { Column = (PlanetColumn) colIndex, Value = value} ))
    .ToLookup(prop => prop.Column, prop => prop.Value);

var planetOrders = lookup[PlanetColumn.Order].ToList();
var planetNames = lookup[PlanetColumn.Name].ToList();
var planetColors = lookup[PlanetColumn.Color].ToList();

Note: I added the enum declaration just because it looks cleaner, you can do it with the integer value directly (and use lookup[0], lookup[1], and lookup[2])

edited Aug 3, 2017 at 5:56

answered Aug 3, 2017 at 5:50

Andrés Robinet

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4 Comments

Caius Jard Over a year ago

A good example of how not every problem is a nail, desperate to be pounded by the hammer that is LINQ :)

Andrés Robinet Over a year ago

Well, it depends on input size and what you are going to do next... but yeah, it's probably too much overhead for common scenarios, and the OP would probably need 3 HashSet<string> instances instead of 3 lists if he's going to search for strings in the collections a few times... but hey, I'm an ILookup fanboy :D

Caius Jard Over a year ago

PS, I meant no disrespect to the technical brilliance of your answer, simply to comment that this, IMHO, is one of those situations where the simple loop approach wins out for simplicity, readability, maintain-ability, performance, self-documentation .. etc :)

Andrés Robinet Over a year ago

No offense taken :)

Xavave · Accepted Answer · 2017-08-03 06:26:57Z

1

or with Linq foreach :

        List<string> planetOrder = new List<string>();
        List<string> planetName = new List<string>();
        List<string> planetColor = new List<string>();
       planets.Split(new[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries).ToList().ForEach(p =>
        {
            planetOrder.Add(p.Split(new[] { ' ' })[0]);
            planetName.Add(p.Split(new[] { ' ' })[1]);
            planetColor.Add(p.Split(new[] { ' ' })[2]);
        });

edited Aug 3, 2017 at 6:26

answered Aug 3, 2017 at 5:55

Xavave

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7 Comments

Xavave Over a year ago

I've updated the code so it's in 1 line ; execution time for lookup solution : 70893 ticks, Ben's answer :2097 ticks, for mine : 1999 ticks

Matt McManis Over a year ago

Thanks, I will look all these over.

Matt McManis Over a year ago

This worked well. It is the fastest solution out of the answers?

Xavave Over a year ago

I've tested speed and the answer is yes

Ben Over a year ago

Are you sure? Because you are doing more split operations. How did you tested this? Stopwatcher?

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