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 <= 10000bills[i]will be either5,10, or20.
class Solution { public boolean lemonadeChange(int[] bills) { int rem5 = 0, rem10 = 0; for(int i = 0; i < bills.length; i++) { int cur = bills[i]; if(cur == 5) rem5++; else if(cur == 10) { rem10++; if(--rem5 < 0) return false; } else if(cur == 20) { if(rem5 == 0) return false; if(rem10 == 0) { if(rem5 < 3) return false; else rem5 -= 3; } else { --rem10; --rem5; } } } return true; } }
simulation, 注意15 = 3 * 5/ 10 + 5