Leetcode 刷题笔记1 贪心算法part03

leetcode 134 加油站

# 索引在列表里循环
index = (index + 1) % len(cost)

class Solution:
    def canCompleteCircuit(self, gas: List[int], cost: List[int]) -> int:
        curSum = 0
        totalSum = 0
        start = 0
        for i in range(len(cost)):
            curSum += gas[i] - cost[i]
            totalSum += gas[i] - cost[i]
            if curSum < 0:
                curSum = 0
                start = i + 1
        if totalSum < 0:
            return -1
        return start

 leetcode 135 分发糖果

先考虑从左到右，在考虑从右到左

class Solution:
    def candy(self, ratings: List[int]) -> int:
        n = len(ratings)
        candies = [1] * n
        for i in range(1, n):
            if ratings[i] > ratings[i - 1]:
                candies[i] = candies[i - 1] + 1
        for i in range(n - 2, -1, -1):
            if ratings[i] > ratings[i + 1]:
                candies[i] = max(candies[i], candies[i + 1] + 1)
        return sum(candies)

leetcode 860 柠檬水找零

简单题

class Solution:
    def lemonadeChange(self, bills: List[int]) -> bool:
        five = 0
        ten = 0
        twenty = 0
        for bill in bills:
            if bill == 5:
                five += 1
            if bill == 10:
                if five <= 0:
                    return False
                ten += 1
                five -= 1
            if bill == 20:
                if five > 0 and ten > 0:
                    five -= 1
                    ten -= 1
                elif five >= 3:
                    five -= 3
                else:
                    return False
        return True

leetcode 406 根据身高重建队列

 先根据身高进行第一波降序排序，第二次对数组进行插入操作

class Solution:
    def reconstructQueue(self, people: List[List[int]]) -> List[List[int]]:
        people.sort(key = lambda x: (-x[0], x[1]))
        que = []
        for i in people:
            que.insert(i[1], i)
        return que