1518. Water Bottles

Easy

There are numBottles water bottles that are initially full of water. You can exchange numExchange empty water bottles from the market with one full water bottle.

The operation of drinking a full water bottle turns it into an empty bottle.

Given the two integers numBottles and numExchange, return the maximum number of water bottles you can drink.

Example 1:

• Input: numBottles = 9, numExchange = 3
• Output: 13
• Explanation: You can exchange 3 empty bottles to get 1 full water bottle. Number of water bottles you can drink: 9 + 3 + 1 = 13.

Example 2:

• Input: numBottles = 15, numExchange = 4
• Output: 19
• Explanation: You can exchange 4 empty bottles to get 1 full water bottle. Number of water bottles you can drink: 15 + 3 + 1 = 19.

Constraints:

• 1 <= numBottles <= 100.
• 2 <= numExchange <= 100

Solution:

class Solution {

    /**
     * @param Integer $numBottles
     * @param Integer $numExchange
     * @return Integer
     */
    function numWaterBottles($numBottles, $numExchange) {
        $totalDrunk = 0;
        $emptyBottles = 0;

        while ($numBottles > 0) {
            // Drink all the current full bottles
            $totalDrunk += $numBottles;

            // Collect the empty bottles
            $emptyBottles += $numBottles;

            // Exchange the empty bottles for new full ones
            $numBottles = floor($emptyBottles / $numExchange);
            $emptyBottles = $emptyBottles % $numExchange;
        }

        return $totalDrunk;
    }
}

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