Highest population

solution.py

def most_populated(births, deaths):
    b = dict((i, births.count(i)) for i in births)
    d = dict((i, deaths.count(i)) for i in deaths)
    alive = 0
    years = {}
    for year in range(min(births), max(deaths)):
        alive = alive + b.get(year, 0) - d.get(year, 0)
        years[year] = alive
    max_year = max(years.values())
    return [key for key, val in years.iteritems() if val == max_year]

births = [18, 0, 10, 4, 16, 2, 16]
deaths = [30, 12, 22, 19, 28, 20, 28]

print most_populated(births, deaths)
# Given a group of people with their birth years and death years, find the year with the highest population.

# *Input*: an array of _n_ birth years, `births`, an array of _n_ death years, `deaths` corresponding to the person's birth year. 
# *Required output*: an array, `years`, containing the year(s) with the highest population
# births [18, 0, 10, 4, 16, 2, 16]
# deaths [30, 12, 22, 19, 28, 20, 28]