FourSeventy

require 'benchmark'
require 'set'


#Determines which customers have paid their monthly balance
#by comparing them to a list of known paid customers.
#O(n^2) solution
def example1
  paid_customers = get_huge_array_of_customers
  customers = get_huge_array_of_customers

FourSeventy

# netcat port scanning
nc -zv host-name port-range
sudo nc -zv -w 2 10.150.0.3 1-1023

#find out what process is using what port
lsof -i :port
sudo lsof -i :80

#list what ports a process is using
lsof -Pan -p PID -i