What is the maximum number of clues in Sudoku?

There is a solvable puzzle with at most 21 clues for every solved grid, with the largest minimal puzzle found so far has 40 clues in the 81 cells. Similar results are known for variants and smaller grids.

How many clues are there in Sudoku?

Puzzles must have at least 17 clues to have a valid solution.

What is the maximum number of Sudoku combinations?

There are exactly 6, 670, 903, 752, 021, 072, 936, 960 possible solutions to Sudoku (about 10^21) . That's far more than can be checked in a reasonable period of time.

What is 77 clue Sudoku?

77 is the maximum number of clues that can still yield an ambiguous sudoku. The "rectangle" method--which provides 77 clues but leaves out two pairs of rectangular corner numbers to create an ambiguous sudoku--works not just for 1s and 2s but for any pair of opposite corner numbers.

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).

17 and Sudoku Clues - Numberphile

Is there 16 * 16 Sudoku?

16 x 16 sudoku puzzles work just the same as regular 9 x 9 sudoku puzzles, but they are, well, a lot bigger! Infact whereas a normal sudoku has 81 squares in it, a 16x16 sudoku has 256 squares in it, so you get a lot more puzzle for your money.

What is Sudoku 4 cell rule?

Rules of Quadruple Sudoku

The object of the puzzle is to fill in the whole 9x9 grid with numbers 1 through 9 (one number per cell) so that each row, each column, and each of the nine 3x3 boxes contains all the nine different numbers 1 through 9. The clues are in the form of sets of four special clue-numbers.

What are the 159 rules 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 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.

Is guessing OK in Sudoku?

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.

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.

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.

Who invented Sudoku?

Sudoku Puzzle Creator Maki Kaji Dies At 69 Known as the "Godfather of Sudoku," Kaji created the puzzle to be easy for children and others who didn't want to think too hard.

What is the rule of 3 Sudoku?

If three candidates can be found in only the same three Cells of a region (Row, Column or Square), then one of these candidates is the solution for the first of these Cells, a second one is the solution for the second Cell and the last candidate is the solution for the third Cell.

Can you solve Sudoku mathematically?

In fact, mathematical thinking in the form of logical deduction is very useful in solving Sudokus. The most basic strategy to solve a Sudoku puzzle is to first write down, in each empty cell, all possible entries that will not contradict the One Rule with respect to the given cells.

Is Sudoku always 3x3?

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.

Is there 0 in Sudoku?

The cool thing about this enigma is that only two possible answers can fill each blank: zero and one—and each grid has a sole solution.

What is the fewest clues in Sudoku?

The fewest clues required for a proper Sudoku is 17, but not all completed grids can be reduced to a proper 17 clue Sudoku. About 49,000 unique (non-equivalent) Sudokus with 17 clues have been found. (A proper Sudoku has only one solution).

What is Sudoku Killer level?

Hard Killer Sudoku levels have the same rules as any other level, the only difference is very few numbers on the grid from the beginning. This makes the game pretty hardcore and requires longer playing time to fill out all the numbers.

What is not allowed in Sudoku?

You can use only numbers from 1 to 9. Each 3×3 block can only contain numbers from 1 to 9. Each vertical column can only contain numbers from 1 to 9. Each horizontal row can only contain numbers from 1 to 9.

What is the knight's rule in Sudoku?

The puzzle is called the Miracle Sudoku and it's made by fellow puzzle legend Mitchell Lee. And here are the special rules: “Any two cells separated by a knight's move or a king's move (in chess) cannot contain the same digit. Any two orthogonally adjacent cells cannot contain consecutive digits.”

Can Sudoku be 4x4?

There are many different sudoku variations. 4x4 sudoku is one of them. It has four rows, four columns and four boxes where the classic version has nine rows, nine columns and nine boxes. The 4x4 version is often called "sudoku for kids" because they are much simpler puzzles to solve.

What is the red number in Sudoku?

There are three squares which contain only three values: 4, 6, and 8. If these numbers were written in any square where they are red, it would be impossible to complete the squares where they are blue. Therefore, the numbers in red can be erased.

Is Sudoku always 9x9?

The given board contains only digits 1–9 and the character '. ' . You may assume that the given Sudoku puzzle will have a unique solution. The given board size is always 9x9.