pascal.cs

using System;
using System.Collections.Generic;
using System.Linq;
using NUnit.Framework;

namespace triangle
{
    public class Pascal
    {
        public static string GenerateNicely(int maxDepth)
        {
            var triangle = Generate(maxDepth);
            return Pretty(triangle);
        }

        public static List<int[]> Generate(int maxDepth)
        {
            var lines = new List<int[]>();

            for (var currentDepth = 0; currentDepth < maxDepth; currentDepth++)
            {
                if (currentDepth == 0)
                {
                    lines.Add(new[] { 1 });
                    continue;
                }

                var thisLine = CreateNewLine(currentDepth);
                PopulateMiddleParts(lines, thisLine, currentDepth);
                lines.Add(thisLine);
            }

            return lines;
        }

        private static int[] CreateNewLine(int i)
        {
            var thisLine = new int[i + 1];
            thisLine[0] = 1;
            thisLine[i] = 1;
            return thisLine;
        }

        private static void PopulateMiddleParts(List<int[]> lines, int[] thisLine, int currentDepth)
        {
            var previous = lines.Last();
            for (var position = 1; position <= currentDepth - 1; position++)
            {
                thisLine[position] = previous[position - 1] + previous[position];
            }
        }

        private static string Pretty(IEnumerable<int[]> triangle)
        {
            var linesWithFixedSpaces = triangle.Select(x => string.Join("    ", x)).ToArray();
            var widest = linesWithFixedSpaces.Max(x => x.Length);

            for (var i = 0; i < linesWithFixedSpaces.Length; i++)
            {
                var leftPad = (widest - linesWithFixedSpaces[i].Length) / 2;
                linesWithFixedSpaces[i] = new string(' ', leftPad) + linesWithFixedSpaces[i];
            }

            var formatted = string.Join(Environment.NewLine, linesWithFixedSpaces);
            return formatted;
        }
    }

    [TestFixture]
    public class PascalTests
    {
        [Test]
        public void GivenOneGetOne()
        {
            var triangle = Pascal.Generate(1);

            Assert.That(string.Join(" ", triangle[0]), Is.EqualTo("1"));
        }

        [Test]
        public void GivenMoreThanOneDepth_StartsAndEndsWithOne()
        {
            var triangle = Pascal.Generate(5);

            Assert.That(string.Join(" ", triangle[0]), Is.StringStarting("1"));
            Assert.That(string.Join(" ", triangle[0]), Is.StringEnding("1"));
        }

        [Test]
        public void GivenTwo_TriangleTwoDeepCreated()
        {
            var triangle = Pascal.Generate(2);

            Assert.That(triangle.Count, Is.EqualTo(2));
        }

        [Test]
        public void GivenTwo_TriangleCreatedWithCorrectValues()
        {
            var triangle = Pascal.Generate(2);

            Assert.That(string.Join(" ", triangle[0]), Is.EqualTo("1"));
            Assert.That(string.Join(" ", triangle[1]), Is.EqualTo("1 1"));
        }

        [Test]
        public void GivenThree_TriangleCreatedWithCorrectValues()
        {
            var triangle = Pascal.Generate(3);

            Assert.That(string.Join(" ", triangle[0]), Is.EqualTo("1"));
            Assert.That(string.Join(" ", triangle[1]), Is.EqualTo("1 1"));
            Assert.That(string.Join(" ", triangle[2]), Is.EqualTo("1 2 1"));
        }

        [Test]
        public void GivenFour_TriangleCreatedWithCorrectValues()
        {
            var triangle = Pascal.Generate(4);

            Assert.That(string.Join(" ", triangle[0]), Is.EqualTo("1"));
            Assert.That(string.Join(" ", triangle[1]), Is.EqualTo("1 1"));
            Assert.That(string.Join(" ", triangle[2]), Is.EqualTo("1 2 1"));
            Assert.That(string.Join(" ", triangle[3]), Is.EqualTo("1 3 3 1"));
        }

        [Test]
        public void GivenFour_PrettyPrints()
        {
            var lines = Pascal.GenerateNicely(6)
                              .Split(new[] {Environment.NewLine}, StringSplitOptions.None);

            Assert.That(lines[0], Is.EqualTo("             1"));
            Assert.That(lines[1], Is.EqualTo("           1    1"));
            Assert.That(lines[2], Is.EqualTo("        1    2    1"));
            Assert.That(lines[3], Is.EqualTo("      1    3    3    1"));
            Assert.That(lines[4], Is.EqualTo("   1    4    6    4    1"));
            Assert.That(lines[5], Is.EqualTo("1    5    10    10    5    1"));
        }

    }
}