simple_scripts

A collection of simple, yet useful ruby code examples

Count occurences of element in a collection

a = ['foo', 'bar', 'zzz', 'foo', 'bar', 'ccc']
Hash[a.group_by {|e| e.itself}.map {|k, v| [v.uniq, v.size]}]

Creating a new class in a funky way

MyModel = Class.new do
  def my_method
  end
end
MyModel.new.my_method

Benchmarking anything in realtime

require 'benchmark'
def bench(count, &block)
  Benchmark.realtime do
    count.times { |i| yield(i) }
  end
end

and use it like:

bench(1000) do |i|
"joining strings is fast" << i.to_s
end

Generating array of n elements in javascript

let count = 4;
[...Array(count).keys()]

Binary search in Ruby

ARR = [1,2,3,5,7,9,12,23,34,45,65]
# Find the index of letter in the array
def find(num)
  lowest = 0
  highest = ARR.count

  while lowest < highest do
    middle_index = ((lowest + highest) / 2).floor
    middle_value = ARR[middle_index]
    if num == middle_value
      puts "Index is #{middle_index}"
      break
    elsif num < middle_value
      highest = middle_index - 1
    elsif num > middle_value
      lowest = middle_index + 1
    end
  end
  puts 'No target found'
end

Bubble sort in Ruby

arr = [5,1,4,2,8]
def bubble_sort(arr)
  length = arr.size - 1
  loop do
    swapped = false
    for i in 0..length do
      curr = arr[i]
      nex = arr[i+1]
      if nex && curr > nex
        swapped = true
        arr[i] = nex
        arr[i+1] = curr
      end
    end
    break if swapped == false
  end
  arr
end

Reverse string in Ruby

str = 'string'
str.chars.inject([]) {|arr, char| arr.unshift(char) }.join

Find a pair of elements from array whose sum equals a given number

INPUT = [1,2,3,4,5,6,7,9]
def find_pair(sum)
  start = 0
  finish = INPUT.length-1

  while start < finish
    return "Match: #{INPUT[start]}, #{INPUT[finish]}" if INPUT[start] + INPUT[finish] == sum

    finish -= 1 if INPUT[start] + INPUT[finish] > sum
    start += 1 if INPUT[start] + INPUT[finish] < sum
  end
end

Hamming in Javascript

const strand1 = 'GAGCCTACTAACGGGAT'
const strand2 = 'CATCGTAATGACGGCCT'

let hammingDistance = (strand1, strand2) => {
  let distance = 0;
  const chars1 = strand1.split("");
  const chars2 = strand2.split("");

  for(let char in chars1){
    if(chars1[char] != chars2[char]){
      distance += 1;
    }
  }
  return distance;
}

Flatten an array(basic)

const arr = [1, [2,3,4], [5,6,7], 8, [9], [10, 11, 12], null]
let flat = [];
let flatten = (array) => {
  array.reduce((acc, value) => {
    if(Array.isArray(value)){
      flatten(value);
    } else {
      flat.push(value);
    }
  }, [])
  return flat;
}

Interposing in Ruby

module Enumerable
  def interpose(sep:)
    Enumerator.new do |el|
      items = each
      loop do
        begin
          el << items.next
          el << sep if items.peek
        rescue StopIteration
          break
        end
      end
    end
  end
end