Have you ever thought about the hidden doubles in Sudoku? When I looked at a puzzle, I noticed that many of the numbers had been used twice with just a difference in orientation. Does this mean that there is more than one solution to that puzzle?
The game of Sudoku is often considered tricky to solve, but there are some tricks that can help. One of the most difficult challenges in Sudoku comes from hidden double patterns. As one tries to complete rows or columns, one will notice that certain pairs are only found within the same row or column.
Let’s dig into this one for you to learn how to do it on your own.
Where are the hidden doubles in Sudoku?
The hidden doubles in Sudoku can be found anywhere in your puzzle. With the help of the pencil marking technique, you can find these hidden number candidates in the same inner box or inner grid located in two blank spaces simultaneously.
Finding the correct location of the hidden doubles in Sudoku takes some time, patience, effort, and the proper technique.
At first, you need to familiarize yourself with the basic parts of the Sudoku puzzle to have a general overview of what to do next.
Check out my article about What is hidden single in Sudoku to learn more about this part: https://puzzlingcut.com/what-is-a-hidden-single-in-sudoku-learn-to-find-one-now/.
If you have tried to solve Sudoku at some point in your life, you’ll realize that knowing the basic parts of Sudoku isn’t as important as finishing it.
However, if you want to finish off your Sudoku puzzle in a shorter time, knowing its basics will help you create a great strategy to solve it.
How do you find hidden doubles in Sudoku?
Finding the hidden doubles in Sudoku takes time, effort, patience, and the correct technique for you to notice. For beginners, the pencil marking method is the best to look for hidden doubles.
First, scan the whole Sudoku puzzle to assess how many blank areas are there, what specific number is missing in their row, column, and inner box, and which number should be placed first.
This is an important step that should not be dismissed. So often, especially when you’re a beginner, we tend to put a number candidate in place without even checking its surroundings thus, leading to incorrect number combinations.
Remember to check the number placements in your Sudoku puzzle’s row, column, and inner box before anything else.
Second, use the pencil marking technique. Mark the possible number candidate/s that can be placed in the blank areas.
The pencil marking technique in Sudoku puzzles will allow you to see which possible numbers would be appropriate in a blank area. Also, it’ll give you a chance to remove other numbers that are not suitable to narrow down your choices quickly.
Choose which number you would like to start with to do the pencil marking technique.
Check this example for your reference.
In this example, I chose number 6 because there are more given numbers 6 in the puzzle already after I scan it.
Next, I highlighted the given number 6 by encircling it with red.
After that, I made an imaginary group for the nine inner boxes into three horizontal groups where group 1 is rows 1-3, group 2 is rows 4-6, and group 3 is rows 7-9. In this way, I quickly narrowed down the areas I needed to check and look after.
You see, narrowing the areas using your imagination makes it easier to solve and exercises your mind in the process of eliminating unnecessary options.
Since in group 1, only row 1 and row 3 contain the number 6, it automatically leaves me with row 2 to put another number 6. So with this, I highlighted it in yellow.
Next in group 2, row 4 and row 5 contains the number 6; therefore, row 6 is highlighted with yellow to mark it as an available place for number 6.
There is no yellow highlight for the third group because there is no given number 6. I leave it for a while to check the horizontal arrangement.
In row 8, I already placed number 6 in the color purple because it’s the only place where number 6 can fit it upon checking their horizontal arrangement.
On the other hand, I can also put the number 6 in purple in row 6 because it’s the only place where it can be placed upon checking its horizontal arrangement.
Lastly, I placed number 6 in white color with an asterisk in the available places I highlighted to know that they are one of the possible number candidates in that blank area.
Since I already did the first part for you, you can now try it yourself using the same technique I mentioned a while ago using other numbers.
In this way, the possible number candidates may or may not increase in one area. You will eventually see the “hidden doubles” somewhere in this puzzle as you go along.
Don’t worry if you do not get it in one try. Just practice, practice, and you’ll solve it in no time.
Try looking for the “hidden doubles” in this example.
What is the hidden doubles in Sudoku?
The hidden doubles are two candidates found simultaneously in two blank areas in the same inner box or inner grid. These numbers are “hidden” because you can only see this when you plot numbers using your pencil.
Like hidden singles, hidden doubles should also use the pencil marking technique during scanning and cross-matching methods. In this way, you’ll be able to assess all areas of your puzzle and won’t miss a thing.
Hidden doubles are two number candidates found in blank areas on the same inner box.
One key in solving the Sudoku puzzles is to look for hidden pairs of numbers; this can be done by looking for inner boxes, columns, and rows. By utilizing the three different ways these pairs of numbers can be hidden in sudoku puzzles, you will find that solving them becomes easier and more enjoyable.
Don’t worry too much if you haven’t solved it on the first try. Just keep practicing, and you’ll get there in no time!