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Find the distance between two points

ruby
# the hypotenuse sqrt(x**2+y**2)
distance = Math.hypot(x2-x1,y2-y1)

Zero pad a number

Given the number 42, pad it to 8 characters like 00000042
ruby
42.to_s.rjust(8,"0")
"%08d" % 42

Right Space pad a number

Given the number 1024 right pad it to 6 characters "1024  "
ruby
1024.to_s.ljust(6)

Format a decimal number

Format the number 7/8 as a decimal with 2 places: 0.88
ruby
(7.0/8.0*100).round/100.0
(7.0/8.0).round(2)

Left Space pad a number

Given the number 73 left pad it to 10 characters "        73"
ruby
73.to_s.rjust(10)

Generate a random integer in a given range

Produce a random integer between 100 and 200 inclusive
ruby
randomInt = rand(200-100+1)+100;
rand(100..200)

Generate a repeatable random number sequence

Initialise a random number generator with a seed and generate five decimal values. Reset the seed and produce the same values.
ruby
srand(12345)
first = (1..5).collect {rand}
srand(12345)
second = (1..5).collect {rand}
puts first == second