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Medium Hard Sudoku level 3 Game 15: Step by Step Easy Solution

Medium Hard Sudoku level 3 Game 15: Step by Step Easy Solution

Step by step easy and quick solution to Medium Hard Sudoku level 3 game 15

Medium hard Sudoku level 3 game 15 solved using simple but powerful Sudoku techniques step by step so that you understand clearly how to solve it yourself.

We'll now solve the medium Sudoku level 3 puzzle. First try to solve it before going through the solution.

How to solve Sudoku level 3 hard Sudoku Game 15

You may skip the next section if you are already aware of the strategy. To skip click here.

Strategy of solving a medium hard Sudoku puzzle

As a strategy, we'll always try to get a valid cell by row column scan first, by possible digit analysis or DSA second, and by reduction caused by Cycles third. Cycles are valuable resources and we'll form a Cycle whenever we get the chance, even if it doesn't result in an immediate valid cell hit.

In addition we'll also use other advanced Sudoku techniques of single digit lock, parallel digit scan or X wing whenever we get the chance.

Evaluation of possible digit subsets for all empty cells is often prescribed to do first. We strongly recommend to avoid this time-consuming activity as far as possible and instead go on filling up the empty cells by unique valid digits using appropriate Sudoku techniques.

The Sudoku techniques for solving this 15th medium hard Sudoku level 3 puzzle game are briefly but clearly explained along with the step by step solution. Our powerful Sudoku technique of parallel digit scan played the most important role in solving this medium hard Sudoku in easy steps.

Let's go through the solution of the game.

Solution to Medium Hard Sudoku level 3 game 15 Stage 1: Breakthrough by DSA, Cycles and Parallel digit scan

How to solve Sudoku level 3 hard Sudoku Game 15

Start with easiest row column scan: R7C2 2 scan 2 in R8, R9. R8C8 3 scan 3 in R7, R9. R6C2 3 scan 3 in C1, C3, R5 -- R4C6 3 scan for 3 in R5, R6, C5 -- R1C4 3 scan 3 in R2, C5, C6 -- R3C7 3 scan 3 in R2, R3, C8, C9. R5C2 7 scan 7 in C1, C3. R6C8 8 scan 8 in R4, R5, C7, C9.

R8C8 1 by parallel scan for 1 on R7: 3 Cells out of 4 vacant in R7 eliminated: R7C4, R7C5 eliminated by 1 in bottom middle major square and R7C7 eliminated by 1 in C7. Single digit lock on 1 in R6C5, R6C6 scan 1 in C4, R4 -- R5C3 1 scan 1 in R4C7, lock on 1 in R6.

Note on how to identify a parallel scan possibility: Digit 1 in bottom middle major square has maximum contribution in eliminating two cells of interest. Look for such bulk elimination by the scanned digit in a promising major square.

Cycle (2,5) in R4C1, R6C1 by reduction of other [1,4] from possible digits [1,2,4,5] in these two cells -- Cycle (6,9) in R4C3, R6C3 as leftover in left middle major square.

Cycle (1,6,8) formed in C2 in three cells of top major square by reduction of [2,4] in C2 from possible digits [1,2,4,6,8] in top left major square -- Cycle (5,9) in R8C2, R9C2.

Note on special characteristics of a Cycle: In a 3 digit Cycle of (1,6,8), the possible digits in the three cells of the Cycle must have at least two instances of each digit 1, 6 and 8 for each cell AND no digit other than the three present in the three possible digit subsets. Effectively, this Cycle eliminated [1,6,8] from all other cells of the parent column C2 and the parent major square.

R1C1 4 by reduction of 2 in lock on (2,5) in C1 -- R3C3 2 as leftover digit in the major square -- R9C1 1 as leftover in C1.

R9C3 8 scan 8 in R8 and lock for 8 in Cycle (1,6,8) in C2 -- R8C3 4 as leftover in bottom left major square.

R8C2 9 by parallel scan for 9 on R8: two out of three vacant cells in R8, R8C5, R8C6 eliminated by 9 in C5 and C6 -- R9C2 5 reduction.

R8C6 7 by reduction of 5 in C6 -- R8C5 5 as leftover digit.

Cycle (2,7) in R1C7, R1C8 by DSA reduction of [1,6,8] in these two cells from possible digits [1,2,6,7,8] in R1 -- R1C9 1 by reduction.

Rest next stage.

That's all for this stage. Results shown.

How to solve Sudoku level 3 hard Sudoku Game 15 Stage 1

Solution to the Sudoku level 3 game 15 Stage 2: Breakthrough by Parallel scan and Single digit lock scan

R3C8 5 by parallel scan for 5 on R3: three out of four vacant cells are eliminated for 5: R3C2, R3C5, R3C6 eliminated by 5 in C2, C5 and C6 respectively leaving only R3C8 for 5 -- Cycle (4,9) in R2C7, R2C9 as leftover.

R6C7 5 scan 5 in R5, C8, C9 -- R6C1 2 reduction -- R4C1 5 reduction -- R2C4 5 scan 5 in C5, C6.

Single digit lock on 2 in R2C5, R3C5 formed: scan by lock on 2 in R1, 2 in C6 -- R5C4 2 scan 2 in R6, C6, lock on 2 in C5 -- R5C8 4 by reduction of 6 in C8 from possible digits [4,6] in R5 -- R5C7 6 as leftover -- R9C9 6 scan 6 in C8, C9.

Note: Always lookout for a breakthrough by a single digit lock.

Solution next stage.

Result of actions taken at this stage shown below.

How to solve Sudoku level 3 hard Sudoku Game 15 Stage 2

Solution to Hard Sudoku level 3 game 15 Final Stage 3: All easy picking

R9C3 6 by reduction of [5,9] from possible digits [5,6,9] in R9 -- R9C8 5, R8C9 6, R9C6 9, R8C6 5 by reduction.

R4C3 8 leftover -- R4C4 5, R6C4 8 reduction. R6C9 5 scan 5 in R4, R5, C8.

R5C9 8 scan 8 in R4, C8 -- R5C2 6 reduction -- R6C8 6 scan 6 in R5, C9 -- R6C5 7, R4C5 6 by reduction.

R5C8 7 leftover in C8 -- R5C1 4 reduction -- R4C9 4 leftover in C9.

R4C1 7 scan 7 in C2 -- R4C2 9 leftover in R4 -- R8C2 leftover in C2 -- R8C1 9 leftover among the 81 cell game.

Final solution shown below.

How to solve Sudoku level 3 hard Sudoku Game 15 final Stage 3

Check for the validity of the solution if you need.

End note

Degree of difficulty at this third level of Sudoku medium hard puzzles is less than the proper Sudoku hard puzzles at level 4. Breakthroughs are easier to find, but advanced Sudoku techniques have to be used when needed.

A mainstream hard Sudoku puzzle at level 4 will always have number of filled cells not more than 25. Even a difference of 1 filled cell may make a lot of difference in hardness of Sudoku puzzles when number of filled cells is at this low range.

Other Sudoku game plays you may like to go through at leisure

If you start at beginner level Sudoku solutions and go through higher levels step by step, you should become an Expert Sudoku solver.

Expert Sudoku: Play and learn how to solve harder Expert level Sudoku puzzles. Many of these are extremely difficult to solve with easy to understand detailed solutions.

Hard Sudoku level 4 games: Selected main category of hard Sudoku puzzles with very detailed solutions. Learn hard Sudoku Strategies and Techniques.

New York Times Hard Sudoku games with compact one-step solutions and a few NYT hard Sudoku games with a little more detailed solutions.

Medium Sudoku level 3: With these games, you really grow up from the beginner level. Learning to solve this level of games will give you confidence to solve really hard Sudoku games of higher difficulty level. Don't skip this level of games while still learning Sudoku. These games are with detailed step by step solutions as well.

Next series of game to play are the main category of hard Sudoku level 4 games with detailed solutions.

Beginner level Sudoku: For beginners, Sudoku beginner level 1 and level 2 game solutions are ideal to start with. Learn to solve easiest Sudoku games and the most basic techniques of finding a hidden single by row column scan and a naked single by possible digit subset analysis (DSA).

Enjoy playing Sudoku.