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Dec 11, 2023 · A sudoku puzzle can be very easy, extremely hard, or somewhere in between, depending on the techniques required to solve it. This page estimates the difficulty level of a given puzzle based on the difficulty of the strategies that must be used to solve it.
- Hidden Pairs, Hidden Triples, Hidden Quads Strategy
Hidden quads are pretty rare, and they can be difficult to...
- Y-Wing Strategy
When to Use Y-Wing. Y-Wing starts with a square that...
- Unique Or Multiple Solution Finder
Enter a sudoku puzzle string below (see the Thonky.com...
- Pointing Pairs, Pointing Triples, Intersection Removal Strategy
Example Puzzle. Try solving the following interactive...
- X-Cycles Strategy
X-Cycles is a strategy very similar to Simple Coloring.We...
- Hidden Pairs, Hidden Triples, Hidden Quads Strategy
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To be able to judge the difficulty of a Sudoku, you first need to define "difficulty". The most useful definition seems to rely on the question: How long does it take an "average" solver to solve the puzzle? Making this precise will involve fixing the population of solvers, and setting up some reference.
Jun 25, 2023 · Difficult Sudoku puzzles require a strategic approach. When tackling challenging grids, make sure you’re well-versed in advanced techniques like X-Wing and Swordfish. These methods help identify patterns that allow for the elimination of possibilities and ultimately lead to the correct solution.
- The X-Wing
- The Swordfish
- Forcing Chains
- The Xy-Wing
- Unique Rectangle Type 1
- Nishio
The X-Wing methodis one of the most basic advanced Sudoku strategies. It can also be applied in some intermediate levels, although its incidence is very low in these cases. Its goal is to eliminate candidates. The player can use this strategy when there is one candidate repeated in four cells that form a square or rectangle when mentally connected ...
This strategy helps to eliminate a candidate from cells too. To apply it, the player must find a digit candidate to two cells in the same row, in three different rows. These cells must also be united by column, regardless of the shape they create. Connecting them will result in a closed chain that reveals two sets of possible placements for that di...
Forcing chains is one of the easiest advanced Sudoku strategies to understand. Unfortunately, applying it requires very high levels of concentration and the outcome can be uncertain. When it does work, it gives the player the solution for one cell. To apply a simple forcing chain, there must be cells with only two candidates in the grid. The player...
The XY-Wing is a strategy to remove candidates. It can be applied when there are three cells in the grid, each with only a pair of candidates that share at least one digit among them (e.g. AB/AC/CB). With a bit of mental effort, the player can picture a Y when connecting them, with one cell working as the stem and the remaining as the branches. The...
Any Sudoku puzzle must have only one possible solution. However, at the most extreme levels, the players might find themselves with two. This happens when there is a “deadly pattern”. This pattern happens when there 4 cells with the same pair of candidates facing each other. For it to be “deadly” each set of two cells must also be placed within the...
The Nishio strategy takes its name from professional puzzle player Tetsuya Nishio who is credited with inventing it. Out of all the advanced Sudoku strategies, this is the one that players avoid the most and use only as a last resource as it takes guessing as a premise. Basically, the player must take a cell with two candidates, choose one, and try...
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- Use a pencil. This may seem obvious to you, but some folks don’t do this! It’s possible for adept players to solve easier sudokus with pen, but for harder puzzles it’s going to help a lot if you use pencil.
- Note potential candidates in open squares. Taking notes is mandatory if you’re solving complex puzzles. Write potential candidates down lightly in open boxes.
- Scan the board to process the puzzle. Take a minute to look over the board and take it all in. You’re probably not on a timer here, so don’t rush anything.
- Start with the obvious singles. Naked and hidden singles are the easiest squares to solve. A naked single is when a number can only go in one possible cell.
Extreme Sudoku is the most challenging version of the 9x9 grid puzzle game for the real puzzle masters! It's not just about following the basic rules - you've got to be a puzzle-solving expert and use advanced strategies to crack it.
Play the hardest unlimited free sudoku puzzles online. Choose one of five very difficult levels from Evil to Extreme for a real challenge. Each puzzle has a unique solution and can be solved with pure logic.
