Does Sudoku always have one solution?

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.

Can there be 2 solutions to Sudoku?

A well-formed Sudoku puzzle is one that has a unique solution. 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.

How many solutions a Sudoku has?

There are 6,670,903,752,021,072,936,960 possible solvable Sudoku grids that yield a unique result (that's 6 sextillion, 670 quintillion, 903 quadrillion, 752 trillion, 21 billion, 72 million, 936 thousand, 960 in case you were wondering). That's way more than the number of stars in the universe.

How do you know if Sudoku has multiple solutions?

A sudoku can have multiple or unique solution based on the clues and their positions in the grid. If a sudoku has less than 17 clues then it will definately have mutliple solutions. But if it has 17 or more clues it can have unique or multiple solutions based on the clues positions.

Is there any rule to solve Sudoku?

The rules for sudoku are simple. A 9×9 square must be filled in with numbers from 1-9 with no repeated numbers in each line, horizontally or vertically. To challenge you more, there are 3×3 squares marked out in the grid, and each of these squares can't have any repeat numbers either.

WHY we solve SUDOKU the way we do!

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 the rule of two in Sudoku?

The game of Sudoku consists of a grid of nine rows and nine columns subdivided into nine 3x3 subgrids. It has two basic rules: Each column, each row, and each box (3x3 subgrid) must have the numbers 1 to 9. No column, row or box can have two squares with the same number.

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.

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.

How do you know if a Sudoku is solvable?

Solvable A sudoku puzzle is solvable if there is only one way to fill in a sudoku board to make it valid. Cell A cell is a position on the Sudoku board. Cells contain cell values and pencil-marks (denoted by (n, {a, b, ..., j}) with n the value of the cell and {a, b, ..., j} the set of pencil-marks).

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.

What is the one rule in Sudoku?

Sudoku Rule № 1: Use Numbers 1-9

Within the rows and columns are 9 “squares” (made up of 3 x 3 spaces). Each row, column and square (9 spaces each) needs to be filled out with the numbers 1-9, without repeating any numbers within the row, column or square.

Is Sudoku high IQ?

From this case study it can be concluded that an individual who is skilled at solving Sudoku puzzles likely has a high general IQ. The results of the weak correlation between Sudoku scores and the WAIT test indicates that in some cases a high Sudoku doesn't necessarily mean a high general IQ.

What does it mean if you're really good at Sudoku?

The best Sudoku players know how to cut through the visual clutter of a Sudoku grid and start scanning immediately for the most valuable clues and information that they need – they know how to apply a process to the Sudoku grid where they can see which places are the most promising.

How much time should it take to solve a Sudoku?

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 159 rule in Sudoku?

Normal sudoku rules apply: Each row, column, and region indicated by thick borders in the grid must contain the digits 1 to 9 once each. 159: Digits in column 1 indicate the column in which the digit 1 appears in that row (e.g. if r4c1 is a 6, r4c6 is a 1).

What are the 10 steps to solving Sudoku?

Is 6 minutes good for Sudoku?

5 minutes is more than enough time to jump start your brain, re-evaluate your Sudoku strategy, and develop a new perspective on how to view the Sudoku grid. So “take 5” and give yourself a new chance at solving Sudoku puzzles!

Is 7 minutes good for Sudoku?

The good sudoku time is one where one is able to solve a complex sudoku game which is in itself a combination of 5 or more sudokus. From the competition point of view, the lesser time one takes the better it is. For very hard say 5 to 7 minutes should be great.

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.

What to do when you get stuck in Sudoku?

Check your puzzle for 3 separate rows or columns where a potential digit can only fit into 2 or 3 cells in each. You should be able to connect the cells if you drew lines through the columns and rows. After you connect all of the cells you can erase the potential candidate from any other cells in those rows or columns.

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.