Java

lizncu

class Solution {
  public boolean lemonadeChange(int[] bills) {
    int five = 0, ten = 0;

    for (int i = 0; i < bills.length; i++) {
      if (bills[i] == 5) {
        five++;
      } else if (bills[i] == 10) {
        five--;
        ten++;
      } else if (bills[i] == 20) {
        if (ten == 0) {
          five -= 3;
        } else {
          ten--;
          five--;
        }
      }

      if (ten < 0 || five < 0) {
        return false;
      }
    }

    return true;
  }
}