https://school.programmers.co.kr/learn/courses/30/lessons/12906
def solution(arr):
answer = []
left = arr[0]
answer.append(left)
for i in range(1, len(arr)):
right = arr[i]
if left != right:
answer.append(right)
left = right
return answer
def solution(arr):
answer = []
for a in arr:
if [a] != answer[-1:]:
answer.append(a)
return answer