What is Sudoku ambiguity rule?

During this process the designer must be careful not to remove two numbers that would cause an ambiguity (where those two numbers could be swapped and the puzzle could be completed two different ways, therefore having two solutions). This is what is called the sudoku ambiguity rule.

What are the 3 rules of Sudoku?

What is the 45 rule in Sudoku?

The 45 rule is a basic solving-technique in Killer Sudoku. Each house (row, column, nonet) must add to 45 (the sum of the digits 1 through 9).

What is Sudoku uniqueness rule?

As an application one has the Uniqueness Argument: Whenever one has a nonempty set of initially open cells, and two candidates at each of those cells, such that among these candidates each value occurs zero or two times in each row, column and block, then the actual solution differs in at least one cell from both ...

What is an example of an unsolvable Sudoku?

Here is an example of a puzzle which can not be solved, consider square Gg, all squares in row G are allocated except for this one, so according to this row Gg must take a 9, as it is the only choice in the row. But Dg is already set to 9 and another 9 can not go in Gg as column g would then have two 9s in it.

Sudoku Primer 139 - TidBits - Unique Rectangles or Ambiguity Rule

Are some Sudoku puzzles unsolvable without guessing?

Can all Sudoku puzzles be solved without guessing? According to Sudoku Of The Day, “Sudoku is a puzzle involving logic—no arithmetic or guessing is required!” While you can, guess, of course, if your guess is wrong, it will throw off the rest of the puzzle and you'll need to start over.

Are Sudokus unsolvable without guessing?

The vast majority of puzzles don't require the trickier techniques, but there are some which just aren't solvable by simple logic alone, and require various forms of guessing to solve.

Can you have 2 solutions to a Sudoku?

A Sudoku puzzle can have more than one solution, but in this case the kind of logical reasoning we described while discussing solving strategies may fall short. There are examples of rank-3 Sudoku puzzles with 17 givens that are well-formed.

What do two dots in Sudoku mean?

Normal sudoku rules apply. White dots between two cells indicate consecutive digits and black dots between two cells indicate a ratio of 1:2.

Is there more than 1 correct answer for Sudoku?

Sudoku is a number puzzle consisting of a 9 x 9 grid in which some cells contain clues in the form of digits from 1 to 9. The solver's jobs is to fill in the remaining cells so that each row, column and 3×3 box in the grid contains all nine digits. There's another unwritten rule: the puzzle must have only one solution.

What is Sudoku rule of 1?

Rule 1 - Each row must contain the numbers from 1 to 9, without repetitions. The player must focus on filling each row of the grid while ensuring there are no duplicated numbers. The placement order of the digits is irrelevant. Every puzzle, regardless of the difficulty level, begins with allocated numbers on the grid.

What is the average Sudoku time?

It is believed that the average Sudoku player spends approximately 20 minutes solving a typical Sudoku puzzle. For very hard puzzles, that number can be much higher. While the game itself can be challenging and complex, several strategies can be used successfully to find the solution.

What is the last possible number rule in Sudoku?

Last possible number is a simple strategy that is suitable for beginners. It is based on finding the missing number. To find the missing number you should take a look at the numbers that are already exist in the 3x3 block you are interested in, and in the rows and columns connected with it.

What is a swordfish in Sudoku?

A Swordfish is a 3 by 3 nine-cell pattern where a candidate is found on three different rows (or three columns) and they line up in the opposite direction. Eventually we will fix three candidates somewhere in those cells which excludes all other candidates in those units.

What is the formula for Sudoku?

For example, in the first and fourth columns beginning from the left of the 9×9 grid, we can form the following equations: m+n=a, g+n+f=g+c. In the second and last rows beginning from the top of the 9×9 grid, the following equations can be formed: b+g+f=a+g, e+n+m=a+b+d.

What is the key to Killer Sudoku?

The 45 Rule

An essential Killer Sudoku solving technique is the "45 rule". This uses the fact that every row, column and block must contain each of the numbers 1 to 9 once. Therefore, the total of all numbers in one row, column or block will always be 45.

Why does the number turn red in Sudoku?

In the highlighted column, number 5 is a candidate in only two cells. Since these are confined to the same group and the solution for this digit, within this column, will forcibly be found between those two cells, number 5 can be eliminated as a candidate to other cells in that group (highlighted in red).

What is a ghost number in Sudoku?

Ghost numbers are empty cells in a row, column or box that are the only cells that can hold a specific digit. Ghost numbers can be used to narrow down the possible places in other rows, columns or boxes where the same digit can exist.

What is a hidden triple in Sudoku?

"Hidden triples" applies when three cells in a row, column, or 3x3 block contain the same three Notes. These three cells also contain other candidates, which may be removed from them. It will be easier to understand this technique if you look at the example. Take a look at the highlighted cells.

Can the same number be in the same spot in Sudoku?

Sudoku puzzles cannot have the same number twice in any row, column or box (container). You can take advantage of this by using deduction to determine (1) which numbers are missing, and (2) where the missing numbers go.

Should I play Sudoku with or without notes?

If you get stuck on Sudoku grid and don't see the obvious solutions for the rest of cells, you should use Notes. With the help of Notes you should fill in all the possible options for each blank cell, focusing on the numbers that are already on the Sudoku grid.

Is there a logic to Sudoku?

Sudoku is a logic-based puzzle. It is a type of constraint satisfaction problem, where the solver is given a finite number of objects (the numerals 1-9) and a set of conditions stating how the objects must be placed in relation to one another.