# 1. 为减少边界条件判断，前后各增加一块空地。注意循环的边界
# 2. 为剪枝，从n开始倒计时
class Solution:
def canPlaceFlowers(self, flowerbed: List[int], n: int) -> bool:
flowerbed = [0] + flowerbed + [0]
res = 0
for i in range(1, len(flowerbed) - 1):
if flowerbed[i] == 0 and flowerbed[i-1] == 0 and flowerbed[i+1] == 0:
res += 1
flowerbed[i] = 1
return n <= res