860.柠檬水找零
class Solution:
def lemonadeChange(self, bills: List[int]) -> bool:
five, ten, twenty = 0, 0, 0
for bill in bills:
if bill == 5:
five += 1
elif bill == 10:
if five <= 0:
return False
five -= 1
ten += 1
elif bill == 20:
if ten > 0 and five > 0:
ten -= 1
five -= 1
twenty += 1
elif five >= 3:
five -= 3
twenty += 1
else:
return False
return True
406.根据身高重建队列
class Solution:
def reconstructQueue(self, people: List[List[int]]) -> List[List[int]]:
# 先按身高降序排，升高相同再按 k 的升序排
people.sort(key=lambda x:(-x[0], x[1]))
que = []
# 再按 k 插入到 people 数组
for i in people:
que.insert(i[1], i)
return que
452. 用最少数量的箭引爆气球
class Solution:
def findMinArrowShots(self, points: List[List[int]]) -> int:
points.sort(key=lambda x: (x[0], x[1]))
count = 1
for i in range(1, len(points)):
# 不在区间内或者弓箭位置不在区间内
if points[i][0] > points[i-1][1]:
count += 1
else:
# 更新右边界
points[i][1] = min(points[i-1][1], points[i][1])
return count