A simple implementation of count min sketch in ruby

countMinSketch.rb

require 'digest'

class CountMinSketch
    def initialize(width, length, hashes)
        @width = width
        @length = length
        @hashes = hashes
        @table = Array.new(length) { Array.new(width) { 0 } }
    end
    
    def increment(item)
        for row in 0..@length - 1
            hash = @hashes[row]
            index = indexFromHash(hash, item)
            @table[row][index] += 1
        end
    end
    
    
    def getCount(item)
        for row in 0..@length - 1
            hash = @hashes[row]
            index = indexFromHash(hash, item)
            count = @table[row][index]
            result = result ? [result, count].min : count
        end
        result
    end

    def printSketch
        pp @table
    end 

    private 

    def indexFromHash(hash, item)
        hash.digest(item).sum % @width
    end
end


sketch = CountMinSketch.new(3, 3, [Digest::SHA256.new, Digest::MD5.new, Digest::SHA384.new])
item = "item"
anotherItem = "anotherItem"

sketch.increment(item)
sketch.increment(item)
sketch.increment(item)

sketch.increment(anotherItem)
sketch.increment(anotherItem)

sketch.printSketch

puts "item count: #{sketch.getCount(item)} expected: 3"
puts "anotherItem count: #{sketch.getCount(anotherItem)} expected: 2"