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timwie's solution

to Twelve Days in the C# Track

Published at Jul 13 2018 · 2 comments
Instructions
Test suite
Solution

Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Output the lyrics to 'The Twelve Days of Christmas'.

On the first day of Christmas my true love gave to me, a Partridge in a Pear Tree.
On the second day of Christmas my true love gave to me, two Turtle Doves, and a Partridge in a Pear Tree.
On the third day of Christmas my true love gave to me, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
On the fourth day of Christmas my true love gave to me, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
On the fifth day of Christmas my true love gave to me, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
On the sixth day of Christmas my true love gave to me, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
On the seventh day of Christmas my true love gave to me, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
On the eighth day of Christmas my true love gave to me, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
On the ninth day of Christmas my true love gave to me, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
On the tenth day of Christmas my true love gave to me, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
On the eleventh day of Christmas my true love gave to me, eleven Pipers Piping, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.
On the twelfth day of Christmas my true love gave to me, twelve Drummers Drumming, eleven Pipers Piping, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.

Hints

  • Try to capture the structure of the song in your code, where you build up the song by composing its parts.

Source

Wikipedia http://en.wikipedia.org/wiki/The_Twelve_Days_of_Christmas_(song)

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

TwelveDaysTest.cs

// This file was auto-generated based on version 1.1.0 of the canonical data.

using Xunit;

public class TwelveDaysTest
{
    [Fact]
    public void First_day_a_partridge_in_a_pear_tree()
    {
        var expected = "On the first day of Christmas my true love gave to me, a Partridge in a Pear Tree.";
        Assert.Equal(expected, TwelveDays.Recite(1));
    }

    [Fact(Skip = "Remove to run test")]
    public void Second_day_two_turtle_doves()
    {
        var expected = "On the second day of Christmas my true love gave to me, two Turtle Doves, and a Partridge in a Pear Tree.";
        Assert.Equal(expected, TwelveDays.Recite(2));
    }

    [Fact(Skip = "Remove to run test")]
    public void Third_day_three_french_hens()
    {
        var expected = "On the third day of Christmas my true love gave to me, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.";
        Assert.Equal(expected, TwelveDays.Recite(3));
    }

    [Fact(Skip = "Remove to run test")]
    public void Fourth_day_four_calling_birds()
    {
        var expected = "On the fourth day of Christmas my true love gave to me, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.";
        Assert.Equal(expected, TwelveDays.Recite(4));
    }

    [Fact(Skip = "Remove to run test")]
    public void Fifth_day_five_gold_rings()
    {
        var expected = "On the fifth day of Christmas my true love gave to me, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.";
        Assert.Equal(expected, TwelveDays.Recite(5));
    }

    [Fact(Skip = "Remove to run test")]
    public void Sixth_day_six_geese_a_laying()
    {
        var expected = "On the sixth day of Christmas my true love gave to me, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.";
        Assert.Equal(expected, TwelveDays.Recite(6));
    }

    [Fact(Skip = "Remove to run test")]
    public void Seventh_day_seven_swans_a_swimming()
    {
        var expected = "On the seventh day of Christmas my true love gave to me, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.";
        Assert.Equal(expected, TwelveDays.Recite(7));
    }

    [Fact(Skip = "Remove to run test")]
    public void Eighth_day_eight_maids_a_milking()
    {
        var expected = "On the eighth day of Christmas my true love gave to me, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.";
        Assert.Equal(expected, TwelveDays.Recite(8));
    }

    [Fact(Skip = "Remove to run test")]
    public void Ninth_day_nine_ladies_dancing()
    {
        var expected = "On the ninth day of Christmas my true love gave to me, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.";
        Assert.Equal(expected, TwelveDays.Recite(9));
    }

    [Fact(Skip = "Remove to run test")]
    public void Tenth_day_ten_lords_a_leaping()
    {
        var expected = "On the tenth day of Christmas my true love gave to me, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.";
        Assert.Equal(expected, TwelveDays.Recite(10));
    }

    [Fact(Skip = "Remove to run test")]
    public void Eleventh_day_eleven_pipers_piping()
    {
        var expected = "On the eleventh day of Christmas my true love gave to me, eleven Pipers Piping, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.";
        Assert.Equal(expected, TwelveDays.Recite(11));
    }

    [Fact(Skip = "Remove to run test")]
    public void Twelfth_day_twelve_drummers_drumming()
    {
        var expected = "On the twelfth day of Christmas my true love gave to me, twelve Drummers Drumming, eleven Pipers Piping, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.";
        Assert.Equal(expected, TwelveDays.Recite(12));
    }

    [Fact(Skip = "Remove to run test")]
    public void Recites_first_three_verses_of_the_song()
    {
        var expected = 
            "On the first day of Christmas my true love gave to me, a Partridge in a Pear Tree.\n" +
            "On the second day of Christmas my true love gave to me, two Turtle Doves, and a Partridge in a Pear Tree.\n" +
            "On the third day of Christmas my true love gave to me, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.";
        Assert.Equal(expected, TwelveDays.Recite(1, 3));
    }

    [Fact(Skip = "Remove to run test")]
    public void Recites_three_verses_from_the_middle_of_the_song()
    {
        var expected = 
            "On the fourth day of Christmas my true love gave to me, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.\n" +
            "On the fifth day of Christmas my true love gave to me, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.\n" +
            "On the sixth day of Christmas my true love gave to me, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.";
        Assert.Equal(expected, TwelveDays.Recite(4, 6));
    }

    [Fact(Skip = "Remove to run test")]
    public void Recites_the_whole_song()
    {
        var expected = 
            "On the first day of Christmas my true love gave to me, a Partridge in a Pear Tree.\n" +
            "On the second day of Christmas my true love gave to me, two Turtle Doves, and a Partridge in a Pear Tree.\n" +
            "On the third day of Christmas my true love gave to me, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.\n" +
            "On the fourth day of Christmas my true love gave to me, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.\n" +
            "On the fifth day of Christmas my true love gave to me, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.\n" +
            "On the sixth day of Christmas my true love gave to me, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.\n" +
            "On the seventh day of Christmas my true love gave to me, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.\n" +
            "On the eighth day of Christmas my true love gave to me, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.\n" +
            "On the ninth day of Christmas my true love gave to me, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.\n" +
            "On the tenth day of Christmas my true love gave to me, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.\n" +
            "On the eleventh day of Christmas my true love gave to me, eleven Pipers Piping, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.\n" +
            "On the twelfth day of Christmas my true love gave to me, twelve Drummers Drumming, eleven Pipers Piping, ten Lords-a-Leaping, nine Ladies Dancing, eight Maids-a-Milking, seven Swans-a-Swimming, six Geese-a-Laying, five Gold Rings, four Calling Birds, three French Hens, two Turtle Doves, and a Partridge in a Pear Tree.";
        Assert.Equal(expected, TwelveDays.Recite(1, 12));
    }
}
using System.Linq;
using System.Text;

public class TwelveDaysSong
{
	private static readonly string[] Things = {
		"a Partridge in a Pear Tree",
		"two Turtle Doves",
		"three French Hens",
		"four Calling Birds",
		"five Gold Rings",
		"six Geese-a-Laying",
		"seven Swans-a-Swimming",
		"eight Maids-a-Milking",
		"nine Ladies Dancing",
		"ten Lords-a-Leaping",
		"eleven Pipers Piping",
		"twelve Drummers Drumming"
	};

	private static readonly string[] ordinalNumberWords = { 
		"first", "second", "third", "fourth", "fifth", "sixth", 
		"seventh", "eighth", "ninth", "tenth", "eleventh", "twelfth"
	};
		
	public string Verse(int nb)
	{
		var sb = new StringBuilder("On the ");
		sb.Append(ordinalNumberWords[nb - 1]);
		sb.Append(" day of Christmas my true love gave to me, ");

		for (int i = nb; i > 1; i--)
		{
			sb.Append(Things[i - 1]);
			sb.Append(", ");
		}

		if (nb > 1) sb.Append("and ");

		sb.Append(Things[0]);
		sb.Append(".\n");
		return sb.ToString();
	}

	public string Verses(int first, int last)
	{
		return string.Join("\n", Enumerable.Range(first, last - first + 1)
			.Select(i => Verse(i))) + "\n";
	}

	public string Sing()
	{
		return Verses(1, 12);
	}
}

Community comments

Find this solution interesting? Ask the author a question to learn more.
Avatar of MetalKid

I see that you used pascal case on "Things" and camel on "ordinalNumberWords". :)

I'm not sure what "nb" stands for. Could use day?

You can use two separate lists like that, but you could also just use a Dictionary, too.

Other than that, pretty good!

Avatar of jkedgar

One thing that might simplify your code - the StringBuider.Append() function returns the modified StringBuilder, so you can chain them. Instead of sb.Append(Things[i - 1]); sb.Append(", ");

you could do sb.Append(Things[i - 1]).Append(", ");

In Verse() you used a StringBuilder to create your string, but in Verses() you used string concatenation. Wouldn't it be better to use a StringBuilder in Verses()?

You aren't checking for any invalid input, so calling Verse(0) or Verse(13) or Verses(1,64) will crash.

The loop in Verse() only gets executed from verse nb down to verse 2. Can you rearrange your code it so it will get called for all verses? That way there would be less special code for the first verse and I think it would be more readable.

What can you learn from this solution?

A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that you could read more about to improve your understanding?