● 860.柠檬水找零

class Solution:
    def lemonadeChange(self, bills: List[int]) -> bool:
        five=ten=0
        for bill in bills:
            if bill==5:
                five+=1
            elif bill==10:
                five-=1
                ten+=1
            elif bill==20 and ten!=0:
                five-=1
                ten-=1
            else:
                five-=3
            if five<0:
                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]]:
        people=sorted(people,key=lambda x:(-x[0],x[1]))
        res=[]
        for p in people:
            if len(res)<=p[1]:
                res.append(p)
            elif len(res)>p[1]:
                res.insert(p[1],p)
        return res

#这里使用了lambda表达式来定义排序规则，lambda x:(-x[0],x[1])表示对于每个元素x，
首先以-x[0]降序排序，然后以x[1]升序排序。

● 452. 用最少数量的箭引爆气球 

class Solution:
    def findMinArrowShots(self, points: List[List[int]]) -> int:
        if len(points)<0:
            return
        points=sorted(points,key=lambda x:(x[0]))
        res=1
        for i in range(1,len(points)):
            if points[i][0]>points[i-1][1]:
                res+=1
            else:
                points[i][1]=min(points[i][1],points[i-1][1])
        return res