## Let's play Sudoku - Game 6

In this sixth session we will solve the Sudoku game we left as exercise in the last session.

We will spend very little time on what is Sudoku and what are its rules of play. If you want to know please refer to any of our * session 1*,

*or the*

**session 2***.*

**session 3**You may also go through **all our Sudoku for beginner game plays using the links given at the end.**

In today's session we will select the valid cells step by step and in one sitting will list out all the steps through which we have solved the game completely.

*Having gained good experience in playing five games at this level already*, we have decided at the start of game play itself that **we would use only the most basic technique of finding a valid cell and valid digit, that is, the column row cross-scanning**.

We *won't use any other more advanced technique such as digit subset analysis* in any of the steps.

**A Sudoku game board of 81 square cells** comes with a few of the cells already filled up with **valid digits 1 to 9.** The *objective of the game is to fill up rest of the empty cells* following the * basic Sudoku rule of NOT using any of the digits 1 to 9 more than once in any row, column or 9-cell square* (identified by thick borders, there are 9 such 9-cell squares).

At each step when we locate a **valid cell** where **we can put one and only one digit**, we will **identify the cell** by its row number (R1 to R9) suffixed by column number (C1 to c9), mention **the digit**, and mention the **column row scan information** (**or exclusion** if the cell happens to be only one empty in the containing row, column or 9-cell square). Sometimes we will add a remark.

The final result will be shown at the end. If you feel any difficulty at any point, please refer back to our earlier sessions, **session 1,****session *** 2*, or

*.*

**session 3**The **only objective at each step is to find a cell in which one and only one digit can be placed. **This is what we call** a valid cell.**

**Aside:**

**Valid cell and Valid digit:**

*We would repeat the definition of valid digit and the valid cell.*

*We define a VALID digit as the digit you put in an empty cell so that,*

It is the only possible digit which you can put in the cell following the rules of the game.

*As before, the most important objective is, how to find out the cell in which you can put one and only one digit out of the digits 1 to 9.*

*We have used the most basic technique of row column sweep or horizontal-vertical cross-scanning mainly. We have used Exclusion technique wherever we found it possible.*

*We used the concept of a favorable zone as a column or a row or a 9-cell square with high digit occupancy so the number of digits possible to fill up the empty cells in the zone is much less and so by eliminating the few other contenders getting only a single digit for a single cell is that much higher. We have also used digits with high occurrence in the board, that is, the favorable digits to our advantage.*

*For a favorable digit that has appeared, say, in 7 cells out of maximum 9 possible all over the board, finding the rest of the two valid cells for this favorable digit by row-column sweep is generally very easy because of elimination of a large part of the board by its occurrence in most zones.*

### Let's find all the valid cells - the first and final stage

The following is **the game board we would solve in this session**.

These are all the steps.

Valid cell **R1C1 for digit 5** by scan R2, R3 – **cell R9C3, digit 5**, scan C1, C2, R7 – **cell R2C9, digit 7**, scan R1, R3 -- **cell R4C1, digit 7**, scan C2, C3, R5: **digit 7 over** -- **cell R3C4, digit 3**, scan R1, R2 : existing -- **cell R4C6, digit 3, **scan C4 -- **cell R6C4, digit 6**, exclusion – **cell R4C7, digit 6**, scan R5, R6 – **cell R9C5, digit 3**, scan C4, C6, R8 -- **cell R5C1, digit 3**, scan C2, C3 -- **cell R6C9, digit 3**, scan C7, C8, R5, 3 over.

We continue with, **cell R6C3, digit 4**, scan R4, R5, existing -- **cell R2C2, digit 4**, scan C1, C3 -- **cell R1C4, digit 4**, *special scan* C5, R2 -- **cell R2C4, digit 9**, scan C5, C6 -- **cell R5C2, digit 8**, scan R4 -- **cell R6C7, digit 8**, scan C8, C9 -- **cell R4C2, digit 9**, scan C3 -- **cell R4C3, digit 2**, exclusion -- **cell R6C8, digit 2**, exclusion -- **cell R8C1, digit 9**, scan R7, C2 -- **cell R9C9, digit 9**, scan R7, R8 -- **cell R5C8, digit 9**, scan C9 -- **cell R5C9, digit 5**, exclusion -- **cell R8C8, digit 5**, scan C7, C9 -- **cell R7C1, digit 6**, scan C2, C3 -- **cell R8C9, digit 6**, scan R7, C7 -- **cell R9C6, digit 6**, scan R7, R8 -- **cell R2C5, digit 6**, scan R1, C6.

From this point on most of the valid cells will be identified by exclusion -- **cell R9C2, digit 1**, exclusion -- **cell R2C3, digit 1**, scan C1 -- **cell R7C3, digit 8**, exclusion -- **cell R2C6, digit 8**, scan R1 -- **cell R1C5, digit 2**, exclusion -- **cell R8C5, digit 8,** exclusion -- **cell R8C4, digit 2**, exclusion -- **cell R2C1, digit 2**, exclusion -- **cell R3C1, digit 8**, exclusion -- **cell R8C7, digit 1**, C9 -- **cell R7C9, digit 4**, exclusion -- **cell R8C6, digit 4**, exclusion -- **R7C6, digit 1,** exclusion -- **Cell R3C9, digit 2** exclusion -- **cell R3C7, digit 4**, exclusion -- **cell R1C7, digit 9**, exclusion -- **cell R1C8, digit 1**, exclusion. End.

The result is the solved game.

Lastly we leave a game for you to solve.

### A game for you to solve

We leave you here with a new game for you to solve. In our next session we will present its solution and another new game.

Enjoy.

### Other Sudoku game plays at absolute beginner level

**Sudoku beginner level game play 11**

**Sudoku beginner level game play 10**

**Sudoku beginner level game play 9**

**Sudoku beginner level game play 8**

**Sudoku beginner level game play 7**

**Sudoku beginner level game play 6**

**Sudoku beginner level game play 5**

**Sudoku beginner level game play 4**

**Sudoku beginner level game play 3**

**Sudoku beginner level game play 2**

**Sudoku beginner level game play 1**

### Assorted Interesting Sudoku game plays

These Sudoku game solutions are collected from various sources and are found to be interesting. You can get these Sudoku solutions at * Interesting Sudoku *not classified at any hardness difficulty level.

### Second and Third level Sudoku games

You will get links to all the 2nd level Sudoku game solutions at **Second level Sudoku.**

Links to third level Sudoku you will get first at 2nd level game solutions and links to fourth level Sudoku you will get in the 3rd level solutions.

It is **recommended** that without jumping over any of the hardness levels, one should progress through solving higher level Sudoku games strictly step by one step up. For example, you shouldn't play a 3rd level Sudoku game without being comfortable in solving 2nd level games.