A faster way to compare text from different columns - excel

Question

Is there a faster way too compare text/data from different columns? It seems to take longer that desired to execute.
Sub StringCom2()
For Each C In Range("M2:M" & Range("M" & Rows.Count).End(xlUp).Row)
For Each L In Range("X2:X" & Range("X" & Rows.Count).End(xlUp).Row)
If C.Cells.Value = "Audio Accessories" And L.Cells.Value = "Headsets" Then
L.Cells.Offset(0, 18).Value = "Headphones"
End If
Next
Next
For Each C In Range("M2:M" & Range("M" & Rows.Count).End(xlUp).Row)
For Each L In Range("X2:X" & Range("X" & Rows.Count).End(xlUp).Row)
If C.Cells.Value = "Headsets & Car Kits" And L.Cells.Value = "Headsets" Then
L.Cells.Offset(0, 18).Value = "Headsets & Car Kits"
End If
Next
Next
End Sub

Answer 1

You could use "Autofilter()" method of "Range" object
like follows (not by my PC so there may be some typos and or range references/offset to adjust...):
Option Explicit
Sub StringCom2()
With Worksheets("Sheet1") '<--| '<-- change "Sheet1" with your actual sheet name
With .Range("M1:X" & .Cells(.Rows.Count, "M").End(xlUp).Row) '<--| reference its range in columns M:X from row 1 to column "M" last non empty cell row
.AutoFilter field:=1, Criteria1:="Headsets" '<--| filter referenced range on its 1st column ("M") with "Headsets"
.AutoFilter field:=12, Criteria1:="Audio Accessories" '<--|filter referenced range again on its 12th column ("X") with "Audio Accessories"
If Application.WorksheetFunction.Subtotal(103, .Resize(, 1)) > 1 Then .Offset(1, 19).Resize(.Rows.Count - 1, 1).SpecialCells(xlCellTypeVisible) = "Headphones"'<--| write in cells offsetted 19 columns right of the matching ones
.AutoFilter field:=12, Criteria1:="Headsets & Car Kits" '<--|filter referenced range again on its 12th column ("X") with "Headsets & Car Kits"
If Application.WorksheetFunction.Subtotal(103, .Resize(, 1)) > 1 Then .Offset(1, 19).Resize(.Rows.Count - 1, 1).SpecialCells(xlCellTypeVisible) = "Headsets & Car Kits"'<--| write in cells offsetted 19 columns right of the matching ones
End With
.AutoFilterMode = False '<--| show all rows back
End With
End Sub

Answer 2

Give this a try and let me know if it terminates faster:
Option Explicit
Sub StringCom_SlightlyImproved()
Dim C As Range, L As Range
Dim ws As Worksheet
Set ws = ThisWorkbook.Worksheets(1)
With Application
.EnableEvents = False
.ScreenUpdating = False
.Calculation = xlCalculationManual
End With
For Each C In ws.Range("M2:M" & ws.Range("M" & ws.Rows.Count).End(xlUp).Row)
For Each L In ws.Range("X2:X" & ws.Range("X" & ws.Rows.Count).End(xlUp).Row)
If C.Value2 = "Headsets" Then
If L.Value2 = "Audio Accessories" Then L.Offset(0, 18).Value2 = "Headphones"
If L.Value2 = "Headsets & Car Kits" Then L.Offset(0, 18).Value2 = "Headsets & Car Kits"
End If
Next L
Next C
With Application
.Calculation = xlCalculationAutomatic
.ScreenUpdating = True
.EnableEvents = True
End With
End Sub
Changes:
declare all variables to avoid Variants which are slower in performance
turn off unnecessary Excel events, calculation, screen-updating for the sub
bring the two loops together to keep the iterations down
code explicitly
Update:
The following solution should be substantially faster as sheet-access has been limited to a bare minimum. Instead, all calculations / comparisons are completed in memory with variables:
Sub StringCom_Improved()
Dim ws As Worksheet
Dim arrResult As Variant
Dim arrHeadset As Variant
Dim arrAccessories As Variant
Dim i As Long, j As Long, maxM As Long, maxX As Long
Set ws = ThisWorkbook.Worksheets(1)
maxM = ws.Range("M" & ws.Rows.Count).End(xlUp).Row
arrHeadset = ws.Range("M2:M" & maxM).Value2
arrResult = ws.Range("AD2:AD" & maxM).Value2 ' column AD is column M with an offset of 18 columns
maxX = ws.Range("X" & ws.Rows.Count).End(xlUp).Row
arrAccessories = ws.Range("X2:X" & maxX).Value2
For i = LBound(arrHeadset) To UBound(arrHeadset)
For j = LBound(arrAccessories) To UBound(arrAccessories)
If arrHeadset(i, 1) = "Headsets" Then
If arrAccessories(j, 1) = "Audio Accessories" Then arrResult(i, 1) = "Headphones"
If arrAccessories(j, 1) = "Headsets & Car Kits" Then arrResult(i, 1) = "Headsets & Car Kits"
End If
Next j
Next i
ws.Range("AD2:AD" & maxM).Value2 = arrResult
End Sub

Answer 3

The faster way is to use Excel formulas
Sub StringCom2()
m = Range("M" & Rows.Count).End(xlUp).Row
x = Range("X" & Rows.Count).End(xlUp).Row
Set r = Range("X2:X" & x).Offset(, 18)
r.Formula = "= If( CountIf( M2:M" & m & " , ""Headsets"" ) , " & _
" If( X2 = ""Audio Accessories"" , ""Headphones"", " & _
" If( X2 = ""Headsets & Car Kits"" , X2 , """" ) , """" ) , """" ) "
r.Value2 = r.Value2 ' optional to replace the formulas with the values
End Sub