860. Lemonade Change

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If possible, giving change with a $10 bill is always better than two $5 bills

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Initialize two variables to keep track of the number of $5 and $10 bills (count5, count10)
If the customer pays with a $5 bill, there’s nothing to do - just increase count5 by 1.
If the customer pays with a $10 bill, there is only one way to give change - decrease count5 by 1 and increase count10 by 1
If the customer pays with a $20 bill:
- If we can give change using one $10 bill and one $5 bill, - decrease the count of each by 1.
- Otherwise, decrease count5 by 3.
In each iteration, if count5 becomes less than 0, return false.

class Solution {
      public boolean lemonadeChange(int[] bills) {
        int count5 = 0;
        int count10 = 0;

        for (int bill:bills){
            switch (bill){
                case 10 -> {
                    if (count5 == 0){
                        return false;
                    }
                    count5--;
                    count10++;
                }

                case 20 -> {
                    if (count10 > 0 && count5 > 0){
                        count10--;
                        count5 --;
                    }else if (count5 >= 3){
                        count5-=3;
                    }else{
                        return false;
                    }
                }

                default -> count5 ++;
            }
        }

        return true;
    }

}

class Solution {
   fun lemonadeChange(bills: IntArray): Boolean {
        var count5 = 0
        var count10 = 0

        for (bill in bills){
            when (bill){
                5-> count5++
                10->{
                    if (count5 == 0) return false
                    count5--
                    count10++
                }
                20->{
                    if (count10 > 0 && count5 > 0) {
                        count10--
                        count5--
                    }else if (count5 >=3) count5-=3
                    else return false
                }
            }
        }

        return true
    }
}

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