#Leetcode# 860. Lemonade Change

https://leetcode.com/problems/lemonade-change/

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 don't have any change in hand at first.

Return true if and only if you can provide every customer with correct change.

Example 1:

Input: [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: [5,5,10]
Output: true

Example 3:

Input: [10,10]
Output: false

Example 4:

Input: [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't give change of $15 back because we only have two $10 bills.
Since not every customer received correct change, the answer is false.

Note:

• 0 <= bills.length <= 10000
• bills[i] will be either 5, 10, or 20.

代码：

class Solution {
public:
    bool lemonadeChange(vector<int>& bills) {
        int n = bills.size();
        int n1 = 0, n2 = 0;
        for(int i = 0; i < n; i ++) {
            if(bills[i] == 5) n1 ++;
            else if(bills[i] == 10) n1 --, n2 ++;
            else if(n2 > 0) n2 --, n1 --;
            else n1 -= 3;
            
            if(n1 < 0) return false;
        }
        return true;
    }
};

　　看下午的比赛有贪心 比赛之前就多找找贪心写一下吧 可能心情不是很好也会影响写的代码吧 脑子不是很在线 可以来一个柠檬茶提提神