Shuffle Demo

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Mensa Daily Puzzlers

For over 15 years Mensa Page-A-Day calendars have provided several puzzles a year for my programming pleasure.  Coding "solvers" is most fun, but many programs also allow user solving, convenient for "fill in the blanks" type.  Below are Amazon  links to the two most recent years.

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Problem Description

This is a Beginners level program using an array of numbers representing cards to "deal" random "hands" of a given size.

Background & Techniques

It takes  less than 50 lines of user written code to shuffle an arbitrary "deck" of numbers and
"deal" them a number of "hands" with a number of "cards" per "hand" as specified by the user.

It was prompted by a user who was trying to do this by randomly choosing card  from the deck without choosing duplicates. That is the hard and slow way to do it. The easy way is to shuffle
the deck, randomly arrange the cards and then choosing "handsize" number at a time from top to bottom to represent the hands.

The key trick is the 10 line "Shuffle" procedure which works from the end of an array of numbers swapping each with a randomly chosen number whose position is less than or equal to the position of the number being swapped.

Running/Exploring the Program 

bulletDownload  executable
bulletDownload source 

Suggestions for Further Explorations

 For standard 52 card arrays it would only take a few more lines of code to display card values as [A,2,3,4...10,J,Q,K] suffixed by as [H,D,C,S].  E.g. 2S for 2 of Spades,  KD for King of Diamonds, etc. 


Original:  August 05, 2012

Modified:  May 15, 2018

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