|
| 1 | +# Time: O(n) |
| 2 | +# Space: O(1) |
| 3 | + |
| 4 | +# At a lemonade stand, each lemonade costs $5. |
| 5 | +# |
| 6 | +# Customers are standing in a queue to buy from you, |
| 7 | +# and order one at a time (in the order specified by bills). |
| 8 | +# |
| 9 | +# Each customer will only buy one lemonade and pay with either a $5, $10, |
| 10 | +# or $20 bill. You must provide the correct change to each customer, |
| 11 | +# so that the net transaction is that the customer pays $5. |
| 12 | +# |
| 13 | +# Note that you don't have any change in hand at first. |
| 14 | +# |
| 15 | +# Return true if and only if you can provide every customer |
| 16 | +# with correct change. |
| 17 | +# |
| 18 | +# Example 1: |
| 19 | +# |
| 20 | +# Input: [5,5,5,10,20] |
| 21 | +# Output: true |
| 22 | +# Explanation: |
| 23 | +# From the first 3 customers, we collect three $5 bills in order. |
| 24 | +# From the fourth customer, we collect a $10 bill and give back a $5. |
| 25 | +# From the fifth customer, we give a $10 bill and a $5 bill. |
| 26 | +# Since all customers got correct change, we output true. |
| 27 | +# Example 2: |
| 28 | +# |
| 29 | +# Input: [5,5,10] |
| 30 | +# Output: true |
| 31 | +# Example 3: |
| 32 | +# |
| 33 | +# Input: [10,10] |
| 34 | +# Output: false |
| 35 | +# Example 4: |
| 36 | +# |
| 37 | +# Input: [5,5,10,10,20] |
| 38 | +# Output: false |
| 39 | +# Explanation: |
| 40 | +# From the first two customers in order, we collect two $5 bills. |
| 41 | +# For the next two customers in order, we collect a $10 bill and |
| 42 | +# give back a $5 bill. |
| 43 | +# For the last customer, we can't give change of $15 back |
| 44 | +# because we only have two $10 bills. |
| 45 | +# Since not every customer received correct change, the answer is false. |
| 46 | +# |
| 47 | +# Note: |
| 48 | +# - 0 <= bills.length <= 10000 |
| 49 | +# - bills[i] will be either 5, 10, or 20. |
| 50 | + |
| 51 | + |
| 52 | +class Solution(object): |
| 53 | + def lemonadeChange(self, bills): |
| 54 | + """ |
| 55 | + :type bills: List[int] |
| 56 | + :rtype: bool |
| 57 | + """ |
| 58 | + five, ten = 0, 0 |
| 59 | + for bill in bills: |
| 60 | + if bill == 5: |
| 61 | + five += 1 |
| 62 | + elif bill == 10: |
| 63 | + if not five: |
| 64 | + return False |
| 65 | + five -= 1 |
| 66 | + ten += 1 |
| 67 | + else: |
| 68 | + if ten and five: |
| 69 | + ten -= 1 |
| 70 | + five -= 1 |
| 71 | + elif five >= 3: |
| 72 | + five -= 3 |
| 73 | + else: |
| 74 | + return False |
| 75 | + return True |
0 commit comments