#
#
# 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.


import collections


class Solution(object):
    def lemonadeChange(self, bills):
        """
        :type bills: List[int]
        :rtype: bool
        """
        if not bills:
            return True
        if bills[0] > 5:
            return False

        cashes = collections.defaultdict(int)

        for b in bills:
            cashes[b] += 1
            if b == 10:
                if 5 not in cashes:
                    return False
                cashes[5] -= 1
                if cashes[5] == 0:
                    del cashes[5]
            elif b == 20:
                if 10 in cashes and 5 in cashes:
                    cashes[10] -= 1
                    cashes[5] -= 1
                    if cashes[5] == 0:
                        del cashes[5]
                    if cashes[10] == 0:
                        del cashes[10]
                elif 5 in cashes and cashes[5] >= 3:
                    cashes[5] -= 3
                    if cashes[5] == 0:
                        del cashes[5]
                else:
                    return False

        return True


if __name__ == '__main__':
    print Solution().lemonadeChange([5, 5, 5, 10, 20])
    print Solution().lemonadeChange([5, 5, 10])
    print Solution().lemonadeChange([10, 10])
    print Solution().lemonadeChange([5, 5, 10, 10, 20])
