Description#
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 do not have any change in hand at first.
Given an integer array bills where bills[i] is the bill the ith customer pays, return true if you can provide every customer with the correct change, or false otherwise.
Example 1:
Input: bills = [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: bills = [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 not give the change of $15 back because we only have two $10 bills.
Since not every customer received the correct change, the answer is false.
Constraints:
1 <= bills.length <= 105bills[i] is either 5, 10, or 20.
Solutions#
Solution 1#
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| class Solution:
def lemonadeChange(self, bills: List[int]) -> bool:
five = ten = 0
for v in bills:
if v == 5:
five += 1
elif v == 10:
ten += 1
five -= 1
else:
if ten:
ten -= 1
five -= 1
else:
five -= 3
if five < 0:
return False
return True
|
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| class Solution {
public boolean lemonadeChange(int[] bills) {
int five = 0, ten = 0;
for (int v : bills) {
switch (v) {
case 5 -> ++five;
case 10 -> {
++ten;
--five;
}
case 20 -> {
if (ten > 0) {
--ten;
--five;
} else {
five -= 3;
}
}
}
if (five < 0) {
return false;
}
}
return true;
}
}
|
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| class Solution {
public:
bool lemonadeChange(vector<int>& bills) {
int five = 0, ten = 10;
for (int v : bills) {
if (v == 5) {
++five;
} else if (v == 10) {
++ten;
--five;
} else {
if (ten) {
--ten;
--five;
} else {
five -= 3;
}
}
if (five < 0) {
return false;
}
}
return true;
}
};
|
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| func lemonadeChange(bills []int) bool {
five, ten := 0, 0
for _, v := range bills {
if v == 5 {
five++
} else if v == 10 {
ten++
five--
} else {
if ten > 0 {
ten--
five--
} else {
five -= 3
}
}
if five < 0 {
return false
}
}
return true
}
|
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| function lemonadeChange(bills: number[]): boolean {
let five = 0;
let ten = 0;
for (let bill of bills) {
switch (bill) {
case 5:
five++;
break;
case 10:
five--;
ten++;
break;
case 20:
if (ten !== 0) {
ten -= 1;
bill -= 10;
}
five -= bill / 5 - 1;
break;
}
if (five < 0) {
return false;
}
}
return true;
}
|
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| impl Solution {
pub fn lemonade_change(bills: Vec<i32>) -> bool {
let (mut five, mut ten) = (0, 0);
for bill in bills.iter() {
match bill {
5 => {
five += 1;
}
10 => {
five -= 1;
ten += 1;
}
_ => {
if ten != 0 {
ten -= 1;
five -= 1;
} else {
five -= 3;
}
}
}
if five < 0 {
return false;
}
}
true
}
}
|
