Track five- and ten-dollar bills, preferring a ten plus a five when making fifteen dollars of change because fives are more flexible.
Complexity
O(n) time and O(1) space.
09 Sept 2026•Easy•Go / Python / TypeScript
Lemonade Change
Determine whether exact change can be returned to every lemonade customer in sequence.
Solution files
Go•lemonade-change/solution.go
package main
func lemonadeChange(bills []int) bool {
fives, tens := 0, 0
for _, bill := range bills {
switch {
case bill == 5:
fives++
case bill == 10 && fives > 0:
fives--
tens++
case bill == 20 && tens > 0 && fives > 0:
tens--
fives--
case bill == 20 && fives >= 3:
fives -= 3
default:
return false
}
}
return true
}
Python•lemonade-change/solution.py
class Solution:
def lemonadeChange(self, bills: list[int]) -> bool:
fives = tens = 0
for bill in bills:
if bill == 5: fives += 1
elif bill == 10:
if not fives: return False
fives, tens = fives - 1, tens + 1
elif tens and fives: tens, fives = tens - 1, fives - 1
elif fives >= 3: fives -= 3
else: return False
return True
TypeScript•lemonade-change/solution.ts
function lemonadeChange(bills: number[]): boolean {
let fives = 0;
let tens = 0;
for (const bill of bills) {
if (bill === 5) fives += 1;
else if (bill === 10) { if (fives === 0) return false; fives -= 1; tens += 1; }
else if (tens > 0 && fives > 0) { tens -= 1; fives -= 1; }
else if (fives >= 3) fives -= 3;
else return false;
}
return true;
}