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freddie2025's solution

to Spiral Matrix in the C# Track

Published at Feb 07 2020 · 0 comments
Instructions
Test suite
Solution

Note:

This exercise has changed since this solution was written.

Given the size, return a square matrix of numbers in spiral order.

The matrix should be filled with natural numbers, starting from 1 in the top-left corner, increasing in an inward, clockwise spiral order, like these examples:

Spiral matrix of size 3
1 2 3
8 9 4
7 6 5
Spiral matrix of size 4
 1  2  3 4
12 13 14 5
11 16 15 6
10  9  8 7

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 SpiralMatrix.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

Reddit r/dailyprogrammer challenge #320 [Easy] Spiral Ascension. https://www.reddit.com/r/dailyprogrammer/comments/6i60lr/20170619_challenge_320_easy_spiral_ascension/

SpiralMatrixTest.cs

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

using Xunit;

public class SpiralMatrixTest
{
    [Fact]
    public void Empty_spiral()
    {
        Assert.Empty(SpiralMatrix.GetMatrix(0));
    }

    [Fact(Skip = "Remove to run test")]
    public void Trivial_spiral()
    {
        var expected = new[,]
        {
             { 1 }
        };
        Assert.Equal(expected, SpiralMatrix.GetMatrix(1));
    }

    [Fact(Skip = "Remove to run test")]
    public void Spiral_of_size_2()
    {
        var expected = new[,]
        {
             { 1, 2 },
             { 4, 3 }
        };
        Assert.Equal(expected, SpiralMatrix.GetMatrix(2));
    }

    [Fact(Skip = "Remove to run test")]
    public void Spiral_of_size_3()
    {
        var expected = new[,]
        {
             { 1, 2, 3 },
             { 8, 9, 4 },
             { 7, 6, 5 }
        };
        Assert.Equal(expected, SpiralMatrix.GetMatrix(3));
    }

    [Fact(Skip = "Remove to run test")]
    public void Spiral_of_size_4()
    {
        var expected = new[,]
        {
             { 1, 2, 3, 4 },
             { 12, 13, 14, 5 },
             { 11, 16, 15, 6 },
             { 10, 9, 8, 7 }
        };
        Assert.Equal(expected, SpiralMatrix.GetMatrix(4));
    }

    [Fact(Skip = "Remove to run test")]
    public void Spiral_of_size_5()
    {
        var expected = new[,]
        {
             { 1, 2, 3, 4, 5 },
             { 16, 17, 18, 19, 6 },
             { 15, 24, 25, 20, 7 },
             { 14, 23, 22, 21, 8 },
             { 13, 12, 11, 10, 9 }
        };
        Assert.Equal(expected, SpiralMatrix.GetMatrix(5));
    }
}
using System;

public class SpiralMatrix
{
	[Flags] 
	public enum Direction
	{
		None 	= 0b0000,
		Right 	= 0b0001,
		Left 	= 0b0010, 
		Down 	= 0b0100, 
		Up 		= 0b1000,
		All 	= 0b1111,
	}
	
    public static int[,] GetMatrix(int size)
    {
		switch (size)
		{
			case 0:
			 	return new int[,] {{}};
          	case 1:	
				return new int[,] {{1}};
			default:
				
				int count = 1, row = 0, col = 0, maxRow = (size -1), maxCol = (size -1), minRow = 1, minCol = 0;
				var output = new int[size , size];
				var direction = Direction.Right;

				output[row, col] = count++;
				
				do
				{
					switch(direction)
					{
						case Direction.Right when col == maxCol:
							direction = ChangeDirection(direction);
							maxCol--;
							break;
						case Direction.Down when row == maxRow:
							direction = ChangeDirection(direction);
							maxRow--;
							break;
						case Direction.Left when col == minCol:
							direction = ChangeDirection(direction);
							minCol++;
							break;
						case Direction.Up when row == minRow:
							direction = ChangeDirection(direction);
							minRow++;
							break;
					}

					switch (direction)
					{
						case Direction.Right: 
							col++;
							break;
						case Direction.Down: 
							row++;
							break;
						case Direction.Left:
							col--;
							break;
						case Direction.Up:
							row--;
							break;
					}

					output[row, col] = count++;
				} 
				while (count <= Math.Pow(size, 2));
		
			return output;
		}

	    static Direction ChangeDirection(Direction direction)
		{
			return direction switch
			{
				Direction.Right => Direction.Down,
				Direction.Down => Direction.Left,
				Direction.Left => Direction.Up,
				Direction.Up => Direction.Right,
				_ => Direction.Right
			};
		}
	}
}

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