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week 02 - day 03 - all cards on deck - arrays and loops #6

Closed rh1456 closed 5 years ago

rh1456 commented 5 years ago

All Cards on Deck!

In this project, you will use JavaScript to model a deck of playing cards. You'll also add functionality to it such as shuffling and dealing.

Shuffling Cards

Computers are notoriously bad at random numbers. This is a pretty deep and complex topic, but it's worth pointing out that most random numbers we use in computing are actually "pseudorandom". For this assignment, you will read about, then implement, a popular algorithm that shuffles the order of a finite set using JavaScript's built-in Math.random() function as a pseudorandom number generator.

Objectives

Requirements

You will model these in code, in any way you see fit. It may require you to experiment and try a number of techniques. There are many valid solutions. Your user interface should consist of a face-down deck, and a face-up "hand" of cards that have been dealt.

Read about, and implement the Fisher–Yates shuffle algorithm:

For our purposes, n is 52:

for i from n - 1 down to 1 do:
  j = random integer (where 0 <= j <= i)
  swap items[i] with items[j]

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Additional Resources

A Hint on Random Numbers

This snippet will give you a random integer, z between 0 and n:

const z = Math.floor(Math.random() * n)

Let's break this down from the inside out:

  1. For this example, assume n is 20.
  2. We use Math.random() to generate a floating-point number between 0 and 1. Let's assume our random value is 0.42.
  3. Multiply that number by n. If we think of this random value as a percentage, multiplying these gives us a number that is some "percentage" of n. Their product is 8.4, or 42% of n.
  4. We use Math.floor() to round down to the nearest whole number, i.e. 8.

Because we're rounding down, it's impossible to get 20. This will give us an integer between 0 and 19. This technique is perfect for finding a "random" index in an array of length n.

Slides

https://slides.com/markdewey-1/arrays-and-loops

rh1456 commented 5 years ago

https://github.com/rh1456/newshuffle