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:
def lemonadeChange(self, bills: List[int]) -> bool:
five, ten = 0, 0
for bill in bills:
if bill == 5:
five += 1
elif bill == 10:
ten += 1
five -= 1
elif bill == 20:
if ten > 0:
ten -= 1
five -= 1
else:
five -= 3
if five < 0:
return False
return Trueclass Solution {
public boolean lemonadeChange(int[] bills) {
int fives = 0, tens = 0;
for (int bill : bills) {
if (bill == 5) {
++fives;
} else if (bill == 10) {
++tens;
if (--fives < 0) {
return false;
}
} else {
if (tens >= 1 && fives >= 1) {
--tens;
--fives;
} else if (fives >= 3) {
fives -= 3;
} else {
return false;
}
}
}
return true;
}
}