Determine if 1 Queen can take King

Question

This challenge was pretty simple - be given the coordinates of a king and a queen on a chess board and determine if the king is in check.

Input is the number of test cases with each test case on a new line, king coordinates first. I read in via text file.

Output "Y" or "N" as the result for each test case.

e.g.

input data:
8
b4 b8
b4 e7
b4 d2
b4 g4
f2 b1
f2 c4
f2 d5
f2 g7

answer:
Y Y Y Y N N N N

I tried a bunch of stuff using System.Text.Encoding to try to figure out how to get the ascii char code from my letters, but ended up falling back on to what I know (Microsoft.VisualBasic).

Option Explicit On
Option Strict On
Option Infer On
Option Compare Text

Imports System.IO
Module Module1

    <STAThread>
    Sub Main()
        Const PATH = "C:\Temp\kingqueen.txt"
        Dim fileContents As String() = System.IO.File.ReadAllLines(PATH)
        Dim numberOfScenarios As Integer = Convert.ToInt32(fileContents(0))
        Dim result As String
        Dim king As String
        Dim queen As String
        For game As Integer = 1 To numberOfScenarios
            king = fileContents(game).Substring(0, 2)
            queen = fileContents(game).Substring(fileContents(game).Length - 2, 2)
            result = result & TestLines(king, queen) & " "
        Next
        result.Trim()
        Console.WriteLine(result)
    End Sub

    Private Function TestLines(ByVal king As String, ByVal queen As String) As String
        Dim kingsub As String = king.Substring(0, 1)
        If king.Substring(0, 1) = queen.Substring(0, 1) Or king.Substring(king.Length - 1, 1) = queen.Substring(queen.Length - 1, 1) Then
            Return "Y"
        Else
            Return TestDiagonals(king, queen)
        End If
    End Function

    Private Function TestDiagonals(ByVal king As String, ByVal queen As String) As String
        Dim kingRank As Integer = Microsoft.VisualBasic.Strings.AscW(king.Substring(0, 1))
        Dim kingFile As Integer = Convert.ToInt32(king.Substring(1, 1))
        Dim queenRank As Integer = Microsoft.VisualBasic.Strings.AscW(queen.Substring(0, 1))
        Dim queenFile As Integer = Convert.ToInt32(queen.Substring(1, 1))

        If (kingRank + kingFile = queenRank + queenFile) Or (kingRank - kingFile = queenRank - queenFile) Then
            Return "Y"
        Else
            Return "N"
        End If
    End Function
End Module    

Answer 1

I would suggest that rather than try parsing strings all through your code, try this.

The code below creates a couple of new things. a numeric coordinate structure, a scenario, which is a pair of coordinates, and a list of scenarios.

There are also a couple of functions to parse the text file and each chess location into coordinates. Further down the line, it makes thing easier when you come to checking the queen and king locations.

Module Module1
    Structure Coord
        Dim Rank As Integer
        Dim File As Integer
    End Structure

    Structure Scenario
        Dim King As Coord
        Dim Queen As Coord
    End Structure

    Dim Scenarios As New List(Of Scenario)
    Dim fileContents() As String
    <STAThread>
    Sub Main()
        Const PATH = "C:\Temp\kingqueen.txt"
        fileContents = System.IO.File.ReadAllLines(PATH)
        ParseTextFile()
        Dim result As String = ""
        For Each testScenario As Scenario In Scenarios
            result = result & TestLines(testScenario) & " "
        Next
        result.Trim()
        Console.WriteLine(result)
        Console.ReadLine()
    End Sub

    Private Function ParsePieceLocationAsCoord(chessCoord As String) As Coord
        Dim tempPoint As New Coord
        tempPoint.File = Asc(chessCoord(0)) - 96
        tempPoint.Rank = Val(chessCoord(1))
        Return tempPoint
    End Function

    Private Sub ParseTextFile()
        Scenarios.Clear()
        For Each line As String In fileContents
            Dim newScenario As Scenario
            newScenario.King = ParsePieceLocationAsCoord(line.Substring(0, 2))
            newScenario.Queen = ParsePieceLocationAsCoord(line.Substring(3, 2))
            Scenarios.Add(newScenario)
        Next
    End Sub

    Private Function TestLines(testScenario As Scenario) As String
        With testScenario
            If .King.Rank = .Queen.Rank Or .King.File = .Queen.File Then
                Return "Y"
            Else
                Return TestDiagonals(testScenario)
            End If
        End With
    End Function

    Private Function TestDiagonals(testScenario As Scenario) As String
        With testScenario
            If (.King.Rank + .King.File = .Queen.Rank + .Queen.File) Or (.King.Rank - .King.File = .Queen.Rank - .Queen.File) Then
                Return "Y"
            Else
                Return "N"
            End If
        End With
    End Function