问题
So i have done how to read a matrix from a text file where the first line defines the elements, however my question is how would i do the opposite that would write to the text file. I would like it to ask the user for the row 0 column 0, and add on, and have this code to write into the console, but do not know how to do into a text file
This is the code to write into console:
Dim size As Integer = 3
Dim numberWidth As Integer = 2
Dim format As String = "D" & numberWidth
Dim A(size - 1, size - 1) As Integer
For i As Integer = 0 To A.GetUpperBound(0)
For j As Integer = 0 To A.GetUpperBound(1)
Console.Write(String.Format("Enter The Matrix Element at A[Row {0}, Col {1}]: ", i, j))
A(i, j) = Convert.ToInt16(Console.ReadLine())
Next
Next
This is code for reading the matrix
Dim path = "d:\matrix.txt"
Dim A(,) As Integer
Using reader As New IO.StreamReader(path)
Dim size = reader.ReadLine() ' read first line which is the size of the matrix (assume the matrix is a square)
Redim A(size - 1, size - 1)
Dim j = 0 ' the current line in the matrix
Dim line As String = reader.ReadLine() ' read next line
Do While (line <> Nothing) ' loop as long as line is not empty
Dim numbers = line.Split(" ") ' split the numbers in that line
For i = 0 To numbers.Length - 1
A(j, i) = numbers(i) ' copy the numbers into the matrix in current line
Next
j += 1 ' increment the current line
line = reader.ReadLine() ' read next line
Loop
End Using
Console.WriteLine("Matrix A :")
Dim numberWidth As Integer = 2
Dim format As String = "D" & numberWidth
For i As Integer = 0 To A.GetUpperBound(0)
Console.Write("| ")
For j As Integer = 0 To A.GetUpperBound(1)
Console.Write("{0} ", A(i, j).ToString(format))
Next
Console.WriteLine("|")
Next
Save function:
Dim A(,) As Integer
Sub SaveMatrix()
Dim path As String = "z:\matrix.txt"
Using fs As New System.IO.FileStream(path, IO.FileMode.OpenOrCreate)
fs.SetLength(0) ' reset file length to 0 in case we are overwriting an existing file
Using sw As New System.IO.StreamWriter(fs)
Dim line As New System.Text.StringBuilder
sw.WriteLine((A.GetUpperBound(0) + 1).ToString()) ' size of array in first line
For i As Integer = 0 To A.GetUpperBound(0)
line.Clear()
For j As Integer = 0 To A.GetUpperBound(1)
line.Append(A(i, j).ToString() & " ")
Next
sw.WriteLine(line.ToString().Trim()) ' output each row to the file
Next
End Using
End Using
Console.WriteLine("")
Console.WriteLine("Matrix successfully saved to:")
Console.WriteLine(path)
End Sub
回答1:
Here's a framework to build upon demonstrating how to enter, save, and load your matrices. You can add other options to the menu based on what other operations you need to implement:
Module Module1
Public A(,) As Integer
Public Sub Main()
Dim response As String
Dim quit As Boolean = False
Do
Console.WriteLine("")
Console.WriteLine("--- Menu Options ---")
Console.WriteLine("1) Enter a Matrix")
Console.WriteLine("2) Display Matrix")
Console.WriteLine("3) Save Matrix")
Console.WriteLine("4) Load Matrix")
Console.WriteLine("5) Quit")
Console.Write("Menu choice: ")
response = Console.ReadLine()
Console.WriteLine("")
Select Case response
Case "1"
EnterMatrix()
Case "2"
DisplayMatrix()
Case "3"
SaveMatrix()
Case "4"
LoadMatrix()
Case "5"
quit = True
Case Else
Console.WriteLine("")
Console.WriteLine("Invalid Menu Choice")
End Select
Loop While (Not quit)
Console.Write("Press any key to dismiss the console...")
Console.ReadKey()
End Sub
Public Sub EnterMatrix()
Dim valid As Boolean
Dim size, value As Integer
Console.Write("Enter the Size of the Square Matrix: ")
Dim response As String = Console.ReadLine()
If Integer.TryParse(response, size) Then
If size >= 2 Then
Console.WriteLine("")
ReDim A(size - 1, size - 1)
For i As Integer = 0 To A.GetUpperBound(0)
Console.WriteLine("--- Row " & i & " ---")
For j As Integer = 0 To A.GetUpperBound(1)
valid = False
Do
Console.Write(String.Format("Enter The Matrix Element at A[Row {0}, Col {1}]: ", i, j))
response = Console.ReadLine()
If Integer.TryParse(response, value) Then
A(i, j) = value
valid = True
Else
Console.WriteLine("")
Console.WriteLine("Matrix Element must be a valid Integer!")
Console.WriteLine("")
End If
Loop While (Not valid)
Next
Console.WriteLine("")
Next
Else
Console.WriteLine("")
Console.WriteLine("Size must be greater than or equal to 2!")
End If
Else
Console.WriteLine("")
Console.WriteLine("Invalid Size")
End If
End Sub
Public Sub DisplayMatrix()
If Not IsNothing(A) AndAlso A.Length > 0 Then
Dim maxLength As Integer = Integer.MinValue
For i As Integer = 0 To A.GetUpperBound(0)
For j As Integer = 0 To A.GetUpperBound(1)
maxLength = Math.Max(maxLength, A(i, j).ToString.Length)
Next
Next
Console.WriteLine("Matrix Contents:")
For i As Integer = 0 To A.GetUpperBound(0)
Console.Write("| ")
For j As Integer = 0 To A.GetUpperBound(1)
Console.Write("{0} ", A(i, j).ToString().PadLeft(maxLength, " "))
Next
Console.WriteLine("|")
Next
Else
Console.WriteLine("The Matrix is empty!")
End If
End Sub
Public Sub SaveMatrix()
If Not IsNothing(A) AndAlso A.Length > 0 Then
Console.Write("Enter the name of the File to Save To (example: `Matrix.txt`): ")
Dim response As String = Console.ReadLine()
Dim fullPathFileName As String = System.IO.Path.Combine(Environment.CurrentDirectory, response)
Try
If System.IO.File.Exists(fullPathFileName) Then
Console.WriteLine("")
Console.WriteLine("There is already a file at:")
Console.WriteLine(fullPathFileName)
Console.WriteLine("")
Console.Write("Would you like to overwrite it? Enter 'Y' or 'YES' to confirm: ")
response = Console.ReadLine.ToUpper
If response <> "Y" AndAlso response <> "YES" Then
Exit Sub
End If
End If
Using fs As New System.IO.FileStream(fullPathFileName, IO.FileMode.OpenOrCreate)
fs.SetLength(0) ' reset file length to 0 in case we are overwriting an existing file
Using sw As New System.IO.StreamWriter(fs)
Dim line As New System.Text.StringBuilder
sw.WriteLine((A.GetUpperBound(0) + 1).ToString()) ' size of array in first line
For i As Integer = 0 To A.GetUpperBound(0)
line.Clear()
For j As Integer = 0 To A.GetUpperBound(1)
line.Append(A(i, j).ToString() & " ")
Next
sw.WriteLine(line.ToString().Trim()) ' output each row to the file
Next
End Using
End Using
Console.WriteLine("")
Console.WriteLine("Matrix successfully saved to:")
Console.WriteLine(fullPathFileName)
Catch ex As Exception
Console.WriteLine("")
Console.WriteLine("Error Saving Matrix!")
Console.WriteLine("Error: " & ex.Message)
End Try
Else
Console.WriteLine("The Matrix is empty!")
End If
End Sub
Public Sub LoadMatrix()
Console.Write("Enter the name of the File to Load From (example: `Matrix.txt`): ")
Dim response As String = Console.ReadLine()
Try
Dim A2(,) As Integer
Dim line As String
Dim value As Integer
Dim values() As String
Dim arraySize As Integer
Dim fullPathFileName As String = System.IO.Path.Combine(Environment.CurrentDirectory, response)
Using sr As New System.IO.StreamReader(fullPathFileName)
line = sr.ReadLine ' get matrix size and convert it to an int
If Integer.TryParse(line, value) Then
arraySize = value
ReDim A2(arraySize - 1, arraySize - 1)
For row As Integer = 0 To arraySize - 1
values = sr.ReadLine().Trim().Split(" ".ToCharArray(), StringSplitOptions.RemoveEmptyEntries)
If values.Length = arraySize Then
For col As Integer = 0 To arraySize - 1
If Integer.TryParse(values(col).Trim, value) Then
A2(row, col) = value
Else
Console.WriteLine("")
Console.WriteLine("Invalid Element in file!")
Exit Sub
End If
Next
Else
Console.WriteLine("")
Console.WriteLine("Invalid Row Size in file!")
Exit Sub
End If
Next
Else
Console.WriteLine("")
Console.WriteLine("Invalid Matrix Size in first line of file!")
Exit Sub
End If
End Using
A = A2
Console.WriteLine("")
Console.WriteLine("Matrix successfully loaded from:")
Console.WriteLine(fullPathFileName)
Catch ex As Exception
Console.WriteLine("")
Console.WriteLine("Error Loading Matrix!")
Console.WriteLine("Error: " & ex.Message)
End Try
End Sub
End Module
回答2:
I have created a class for the Matrix data and the a List(of T) so you con't have to worry about changing the size of an array.
I am using Interpolated strings which is a replacement for String.Format in some cases and easier to read.
I have overriden the .ToString method in the MatrixItem class to make it easy to save the objects to a text file.
Other comments in-line.
Public Sub Main()
Dim A As List(Of MatrixItem) = CreateListOfMatrixItem()
SaveMatrixList(A)
ViewMatrixFile()
Console.ReadLine()
End Sub
Private Function CreateListOfMatrixItem() As List(Of MatrixItem)
Dim A As New List(Of MatrixItem)
Dim HowManyRows As Integer = 3
For i As Integer = 0 To HowManyRows - 1
Dim M As New MatrixItem()
For j As Integer = 0 To 2
Console.WriteLine($"Enter The Matrix Element at A[Row {i}, Col {j}]: ")
Select Case j
Case 0
M.X = Convert.ToInt16(Console.ReadLine())
Case 1
M.Y = Convert.ToInt16(Console.ReadLine())
Case 2
M.Z = Convert.ToInt16(Console.ReadLine())
End Select
Next
A.Add(M)
Next
Return A
End Function
Private Sub SaveMatrixList(A As List(Of MatrixItem))
Dim sb As New StringBuilder
For Each item In A
sb.AppendLine(item.ToString)
Next
'this will open or create the file and append the new data
'if you want to overwrite the contents of the file then
'use File.WriteAllText("Matrix.txt", sb.ToString)
File.AppendAllText("Matrix.txt", sb.ToString)
End Sub
Private Sub ViewMatrixFile()
Dim lines = File.ReadAllLines("Matrix.txt")
Console.WriteLine($"{"X",10}{"Y",10}{"Z",10}")
For Each line In lines
Dim numbers = line.Split(","c)
'To format the values with the a numeric format it is necessary to convert the
'strings to a numeric type.
Console.WriteLine($"{CInt(numbers(0)),10:D2}{CInt(numbers(1)),10:D2}{CInt(numbers(2)),10:D2}")
Next
End Sub
Public Class MatrixItem
Public Property X As Int16
Public Property Y As Int16
Public Property Z As Int16
Public Overrides Function ToString() As String
Return $"{X},{Y},{Z}"
End Function
End Class
来源：https://stackoverflow.com/questions/55324772/writing-a-matrix-to-a-text-file