LeetCode860. Lemonade Change

文章目录

一、题目

At a lemonade stand, each lemonade costs 5. Customers are standing in a queue to buy from you and order one at a time (in the order specified by bills). Each customer will only buy one lemonade and pay with either a 5, 10, or 20 bill. You must provide the correct change to each customer so that the net transaction is that the customer pays $5.

Note that you do not have any change in hand at first.

Given an integer array bills where bills[i] is the bill the ith customer pays, return true if you can provide every customer with the correct change, or false otherwise.

Example 1:

Input: bills = [5,5,5,10,20]

Output: true

Explanation:

From the first 3 customers, we collect three $5 bills in order.

From the fourth customer, we collect a 10 bill and give back a 5.

From the fifth customer, we give a 10 bill and a 5 bill.

Since all customers got correct change, we output true.

Example 2:

Input: bills = [5,5,10,10,20]

Output: false

Explanation:

From the first two customers in order, we collect two $5 bills.

For the next two customers in order, we collect a 10 bill and give back a 5 bill.

For the last customer, we can not give the change of 15 back because we only have two 10 bills.

Since not every customer received the correct change, the answer is false.

Constraints:

1 <= bills.length <= 105

bills[i] is either 5, 10, or 20.

二、题解

cpp 复制代码
class Solution {
public:
    bool lemonadeChange(vector<int>& bills) {
        int n = bills.size();
        vector<int> balance(3,0);
        for(int i = 0;i < n;i++){
            int sub = bills[i] - 5;
            if(sub == 5 && balance[0] == 0) return false;
            else if(sub == 15 && (balance[0] == 0 || (balance[1] == 0 && balance[0] < 3))) return false;
            if(sub == 5) balance[0]--;
            else if(sub == 15){
                if(balance[1] > 0) balance[0]--,balance[1]--;
                else balance[0] -= 3;
            }
            if(bills[i] == 5) balance[0]++;
            else if(bills[i] == 10) balance[1]++;
            else balance[2]++;
        }
        return true;
    }
};

更好的解法

cpp 复制代码
class Solution {
public:
    bool lemonadeChange(vector<int>& bills) {
        int n = bills.size();
        int five = 0,ten = 0,twenty = 0;
        for(int i = 0;i < n;i++){
            if(bills[i] == 5) five++;
            else if(bills[i] == 10){
                if(five == 0) return false;
                ten++;
                five--;
            }
            else if(bills[i] == 20){
                if(five > 0 && ten > 0) five--,ten--;
                else if(five >= 3 && ten == 0) five -= 3;
                else return false;
            }
        }
        return true;
    }
};
相关推荐
元亓亓亓41 分钟前
LeetCode热题100--230. 二叉搜索树中第 K 小的元素--中等
算法·leetcode·职场和发展
草莓熊Lotso41 分钟前
《算法闯关指南:优选算法-双指针》--01移动零,02复写零
c语言·c++·经验分享·算法·leetcode
焜昱错眩..2 小时前
代码随想录算法训练营第三十九天|62.不同路径 63.不同路径ll
算法
ajassi20005 小时前
开源 C++ QT Widget 开发(十五)多媒体--音频播放
linux·c++·qt·开源
焦耳加热5 小时前
阿德莱德大学Nat. Commun.:盐模板策略实现废弃塑料到单原子催化剂的高值转化,推动环境与能源催化应用
人工智能·算法·机器学习·能源·材料工程
wan5555cn5 小时前
多张图片生成视频模型技术深度解析
人工智能·笔记·深度学习·算法·音视频
u6066 小时前
常用排序算法核心知识点梳理
算法·排序
鹅毛在路上了7 小时前
C++, ffmpeg, libavcodec-RTSP拉流,opencv实时预览
c++·opencv·ffmpeg
John_ToDebug7 小时前
定制 ResourceBundle 的实现与 DuiLib 思想在 Chromium 架构下的应用解析
c++·chrome·ui
蒋星熠8 小时前
Flutter跨平台工程实践与原理透视:从渲染引擎到高质产物
开发语言·python·算法·flutter·设计模式·性能优化·硬件工程