Excel Puzzle X Solver

Puzzle X is a fun logic game available on the web. In this post we see how to create a Puzzle X solver with Excel VBA macros. The macro converts the Puzzle X pattern into 1s and 0s that are added along the puzzle in the worksheet. It then loops through rows (or columns) using worksheet functions to search for clues to solve each X in the puzzle. It’s a good example of logic programming. Play Puzzle X online HERE.

Puzzle X

Puzzle X is a logic game where players need to fill cells in a grid with an X so that it is unique within its row and column. The grid can be of different sizes, the larger the grid the more Xs to fill, and therefore the more challenging it is. The goal of the game is to fit all Xs in the shortest time possible. This makes Puzzle X a great exercise to improve cognitive abilities and reduce stress.

The game was created by Excel Macro Mania in 2023. As many of its games and products, Puzzle X was first created in Excel.  The puzzle allowed for almost infinite number of rows and columns but only grids up to 30 rows and columns were used. The layout of a simple puzzle in Excel looks as follows.

 

The web version of Puzzle X was published in 2024 and looks as shown below. Players can choose from six grids of increasing difficulty starting with ten rows and columns (i.e., 10X) up to 20X. It has a timer to track the time it takes to complete. When completed, players can save their nickname and see other users’ scores in a table that pops up underneath the puzzle grid.

 

Layout and pattern

The macro converts the Puzzle X pattern into 1s and 0s that are added along the puzzle in the worksheet. Well, it’s not necessary to add the 0s though, it is enough to count 1s for rows or columns to get the number of empty cells. The following macro loops through the puzzle and adds number 1 for black cells.

  Dim cell As Range
  For Each cell In rng  'rng depends on puzzle size (10X, 12X, ...)
      If cell.Interior.Color = vbBlack Then cell.Value = 1
  Next cell

Numbers are not visible unless changing the font color. They could also be added to another worksheet or to an array, but having the numbers in the worksheet allows to leverage worksheet functions that help identify clues to solve each X in the puzzle (see next).

 

Solving Loops

We need to loop through rows (or columns) and find the gaps where a unique X can be placed in order to solve the entire puzzle. See below the first loop in the solver macro. As we will see later, that will all be put inside another loop to repeat the process (see later Solving Whole Puzzle).

  Dim rng As Range, rngRow As Range  'rng is the range of the puzzle (defined earlier)

  For Each rngRow In rng.Rows
      'solving steps and 2nd loop here (see next)
  Next rngRow

We use a variable inside the loop to track the number of Xs that have been solved while looping. This is used later to select which row (or column) needs to be targeted next. Additionally, a conditional statement using the CountIf worksheet function ensures the solver continues only if the row (or column) is empty (no X yet solved).  Another loop checks next whether the row has the number of black cells for the corresponding number of blanks using the count of cells with content (number 1 previously added to each black cell) and the variable solved. The first time it loops, it looks for a row (or column) with only 1 blank (which is equivalent to a row with 9 black cells for a 10X puzzle).

  Dim solved As Integer

  solved = WorksheetFunction.CountIf(rng, "X")
  If WorksheetFunction.CountIf(rngRow, "X") = 0 Then
      If WorksheetFunction.CountA(rngRow) = n - 1 - solved Then  'where n is the number of Xs to solve
          '2nd loop here (see next)
      End If
  End If

Finally, when all those conditions are met, a second loop moves through each blank cell in that row (or column) and checks whether an X has been placed along the corresponding column (or row) for each cell. If there’s no other X, the macro solves the X in that cell and exits that loop.

  For Each cell In rngRow.Columns.SpecialCells(xlCellTypeBlanks)

      If WorksheetFunction.CountIf(Columns(cell.Column), "X") = 0 Then
          Cells(cell.Row, cell.Column).Value = "X"
          Exit For
      End If
  Next cell

 

Solving Whole Puzzle

The whole process needs to repeat as many times as needed to solve the whole puzzle. The first loop above moves through all rows (or columns) just once. Depending on the design/configuration of the puzzle, that will solve one or more Xs, but most likely not all of them. This loop uses the variable “solved” to check whether the whole puzzle has been solved.

  Do Until solved = n  'where n is the number of Xs to solve

      ‘puzzle solving loops (shown above)
  Loop

This solver can be leveraged to solve puzzles of any size. There are hundreds of puzzles with solutions available in the books below. Additionally, you can play Puzzle X online here. See below the solver Excel file for download, which comes with a few examples and allows to recreate there any puzzle and solve it.

 

Download Excel Puzzle X Solver