330. 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:
Input: bills = [5,5,5,10,20]
Output: true

Example 2:
Input: bills = [5,5,10]
Output: true

Example 3:
Input: bills = [10,10]
Output: false

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