How Can I Solve a Sudoku Puzzle Fast?

You are given a Sudoku with pre-filled numbers in a nine by nine grid.

Medium Sudoku from https://www.createclassicsudoku.com
Medium Sudoku from https://www.createclassicsudoku.com

Your task is to fill all empty squares in this nine by nine grid so that each row/column/box contains nine numbers 1 through 9.

And you know the methods to solve a Sudoku puzzle, including OneChoice, Elimination, Interaction, Subset, X-Wing, XY-Wing, XYZ-Wing, and guessing. You are able to solve Sudoku puzzles. Now, you wonder, how can I solve a Sudoku puzzle fast? What are good practices solving Sudoku puzzles FAST?

If you are in this phase, congratulations! You are exploring the efficiency of solving Sudokus to be an expert Sudoku solver.

When you solve a Sudoku puzzle, you are constantly checking which number should an empty square be, and where an untaken number in a row/column/box goes to.  If this does not work, you write down all the candidate numbers of each empty square and try to refine them using solving methods. To be efficient, you will need to form a routine of solving Sudoku, a routine that is most suitable for you! This routine includes but not limited to

  • Form a routine how you scan the empty squares. Some people prefer checking the empty squares from the top to the bottom, then from the left to right; while others prefer checking empty square with most clues first. Choose the one you like the best.
  • Form a routine how you examine an untaken number in a row/column/box. Some people prefer checking an untaken number that appears the most in the nine by nine grid; while others prefer checking an untaken number exactly from 1 to 9. Choose the one that works the best for you.
  • Form a routine how you use the solving methods.  First, rank the solving methods. Some may think OneChoice is easier than Elimination. While others think Elimination is easier than OneChoice. You need to rank the solving methods based on your preferences.  After ranking the solving methods, you always use the easier solving methods first. An advanced method is used only when all easier methods do not work.
  • Be careful not making mistake. Double check. Every time you fill a number in an empty square, double check. This way you are less likely making mistake.

If you develop a routine that works the best for you, you will certainly solve Sudoku puzzles faster.  For me, I like using OneChoice and Elimination first because these two methods do not need me to write any candidate numbers for each empty square. Only when these two methods do not work, I will write down candidate values for the empty squares. Using this routine, I solve Sudoku puzzles pretty fast!

Author: ZZ

Yaling Zheng, Ph.D., founder of https://www.createclassicsudoku.com, received a doctorate degree from the University of Nebraska-Lincoln, where her studies focused on constraint programming and machine learning. She lives in Greater Cleveland/Akron.