Tool to solve countdown numbers games automatically. The Numbers Round in the TV Game Show Countdown is a number games which objective is to get a number with the four elementary operators (+, -, ×, ÷) and a list of randomly picked numbers.

Countdown Numbers Game - dCode

Tag(s) : Number Games

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To find the solutions of a **countdown number game**, the only method is to make all possible math calculations with the starting tiles (dCode use this method).

The general principle is to start with the list of `N` numbers, pick `2` and make all operations with these two numbers, if the result is the expected total, note the calculation as possible solution, else, store the result in the list and try again with the `N-1` new numbers in the list, and so on.

__Example:__ Numbers `2,6,10`, then for each couple among `(2,6),(2,10),(6,10)`, let's take `(2,6)`, make the calculations `2+6=8`, `2*6=12`, `6-2=4` and `6/2=3` to get 4 new numbers `(8,12,4,3)` that will make 4 new couples with the remaining `10`: `(8,10)`, `(12,10)`, `(4,10)` and `(3,10)`. Start over with new couples recursively.

The **original solver** uses the rules of the TV **Countdown** gameshow with 6 number tiles (all natural integers not null), calculations use `+`, `-`, `*`, `/` operators but avoid non integer divisisions (leading to decimal numbers).

__Example:__ Find `123` with `4,5,6,7,8,9`. In 3 operations:`8 + 5 = 13; 13 x 9 = 117; 117 + 6 = 123`.

The **advanced solver** allows more options, constraints on operators, number of operations, etc. It also proposes to generate a list of all possible results from given numbers.

__Example:__ Find `24` by using all numbers `5,5,5,1` and allowing non integers values:`1 / 5 = 0.2; 5 - 0.2 = 4.8; 5 x 4.8 = 24`

The **N-Numbers solver** uses original rules but with any quantity of numbers. Given result is not the easiest one, a random one. Calculation can be very long, billions of iterations, and if there is no answer, it will never end.

There are three main type of algorithms for solving this number game:

__Example:__ The numbers are 2, 5, 10

Recursive search: make all calculation with N numbers. It uses 2 numbers and for each operation, retry with the results and the N-2 remaining numbers.

__Example:__ Take 2 and 5, make an addition: 2+5=7, a subtraction, 5-2 = 3, etc. Take the result 7 (ou 3), and unused numbers: 10, and start over. 7+10 = 17, etc.

Search with cache: same as the previous one, but stores the calculation to avoid remake them, so, slightly faster, but necessitate a lot of memory.

__Example:__ Take 2 and 5, see if results are already known for addition 7, and subtraction 3, etc. Go on more quickly.

Random search: can find a solution quickly but do not make all calculations, it can prove that a solution exists, but not that a solution does not exist.

__Example:__ Take 2 random numbers 5 and 10, make a random operation: multiplication, store the result: 5*10=50 and go on with remaining results: 2 and 50

Negative numbers are ignored because they do not influence resolution. Indeed apply the operator `-` (minus) in front of any negative number to make it positive.

__Example:__ Numbers `3,2,-1` and target `7`, calculate `3*2-(-1)=7`

__Example:__ Numbers `3,2,1` and target `7`, calculate `3*2+=7`

The physical versions of the game have 24 tiles

1 to 10 | 2 copies |

25, 50, 75 and 100 | 1 copy |

The game is ideal for learning how to do calculations in school classes. The board game is available here (link)

dCode retains ownership of the online "Countdown Numbers Game" source code. Except explicit open source licence (indicated CC / Creative Commons / free), the "Countdown Numbers Game" algorithm, the applet or snippet (converter, solver, encryption / decryption, encoding / decoding, ciphering / deciphering, translator), or the "Countdown Numbers Game" functions (calculate, convert, solve, decrypt / encrypt, decipher / cipher, decode / encode, translate) written in any informatic language (Python, Java, PHP, C#, Javascript, Matlab, etc.) and all data download, script, copy-paste, or API access for "Countdown Numbers Game" are not public, same for offline use on PC, tablet, iPhone or Android ! Remainder : dCode is free to use.

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- 6 Numbers Game Solver (Original)
- 6 Numbers Game Solver (Improved)
- N-Numbers Game Solver
- How to solve a countdown numbers game?
- Which solver to use?
- What are the most common algorithms for countdown game?
- How to use negative numbers?
- What is the distribution of tiles / numbers?
- How to play Countdown Number Game at school?

countdown,right,count,letter,calculation,addition,subtraction,multiplication,division,operation,plus,minus,1,2,3,4,5,6,7,8,9,10,25,50,75,100,mathematic,math,find,number,sign

Source : https://www.dcode.fr/countdown-numbers-game

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