Coding interview problem : returns the same numbers present in each given list.

intersections_between_arrays.py

# Find the numbers that appear in all arrays.
# Return them as a list.
#
# Input :
# [2, 6, 9, 11, 13, 17]
# [3, 6, 7, 10, 13, 18]
# [4, 5, 6, 9, 11, 13]
#
# Output must be :
# [6, 13]

def intersectValues(lists):
	k = len(lists)
	hashtable = {}
	output = []
	for lc in range(0, len(lists)):
		list = lists[lc]
		for i in range(0, len(list)):
			number = list[i]
			if number not in hashtable:
				hashtable[number] = []
				for a in range(0, k):
					hashtable[number].append(1 if a == lc else 0)
			else:
				if hashtable[number][lc] == 0:
					hashtable[number][lc] = 1
	for number in hashtable:
		if min(hashtable[number]) == 1:
			output.append(number)
	return output

print intersectValues([[2, 6, 9, 11, 13, 17], [3, 6, 7, 10, 13, 18], [4, 5, 6, 9, 11, 13]])