Problem 6.1
Find Duplicates
Write a function dups
that takes a list of values as argument and finds all the elements that appear more than once in the list.
>>> dups([1, 2, 1, 3, 2, 5])
[1, 2]
>>> dups([1, 2, 3, 4, 5])
[]
>>> dups([1, 1, 1, 1])
[1]
Solution
def dups(numbers):
seen = []
result = []
for n in numbers:
if n in seen and n not in result:
result.append(n)
seen.append(n)
return result