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
沐怡旸6 分钟前
【底层机制】std::unique_ptr 解决的痛点?是什么?如何实现?怎么正确使用?
c++·面试
感哥41 分钟前
C++ 内存管理
c++
聚客AI1 小时前
🙋‍♀️Transformer训练与推理全流程:从输入处理到输出生成
人工智能·算法·llm
大怪v3 小时前
前端:人工智能?我也会啊!来个花活,😎😎😎“自动驾驶”整起!
前端·javascript·算法
惯导马工5 小时前
【论文导读】ORB-SLAM3:An Accurate Open-Source Library for Visual, Visual-Inertial and
深度学习·算法
骑自行车的码农7 小时前
【React用到的一些算法】游标和栈
算法·react.js
博笙困了7 小时前
AcWing学习——双指针算法
c++·算法
感哥7 小时前
C++ 指针和引用
c++
moonlifesudo7 小时前
322:零钱兑换(三种方法)
算法
感哥18 小时前
C++ 多态
c++