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Java-based LeetCode algorithm problem solutions, regularly updated
860\. Lemonade Change
Easy
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`.