Synopsis

To validate if a cell value is valid within the puzzle, we have to do three checks:

• Is the value unique within the Row
• Is the value unique within the Column
• Is the value unique within the Box

To begin to code this, we have to identify the steps needed to fine non-unique instances, or collisions

• Find first cell in the current row, iterate each next-cell until we get to the last cell in the row
• Do the same for columns, first cell in column, iterate each next cell in the column until we get to the last cell in the column
• Finally for the box, find the first cell in the box, iterate each next cell in the box until we get to the last cell in the box.
• Keep track of all collisions as you iterate

Code Design

• CheckCollisionsInrow
  
  • getFirstCellInRow
  • getNextCellInRow
  • getLastCellInRow
• CheckCollisionsInColumm
  
  • getFirstCellInColumn
  • getNextCellInColumn
  • getLastCellInColumn
• CheckCollionsInBox
  
  • getFirstCellInBox
  • getNextCellInBox
  • getLastCellInBox

Take Aways

A step-by-step approach on how we recognize valid cells within the puzzle leads to an algorithm which we can code from