year_max_pop.py

'''
Given a list of people with their birth and end years,
between a specific start year and end year, 
find the year with the most number of people alive.
'''
import numpy as np

def year_max_pop(people, start_year, end_year):
	n_years = end_year - start_year + 1
	pops = np.zeros(n_years)
	for birth, death in people:
		assert birth <= death
		idx = [i - 1900 for i in range(birth, death + 1)]
		pops[idx] += 1
	return np.argmax(pops) + 1900

people = [[1900, 1988], [1932, 2000], [1957, 1957], 
		  [1956, 1999], [1935, 1945], [1920, 1944], 
		  [1998, 2000]]
assert year_max_pop(people, 1900, 2000) == 1935