[LeetCode] 1518. Water Bottles

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

换水问题。

超市正在促销，你可以用 numExchange 个空水瓶从超市兑换一瓶水。最开始，你一共购入了 numBottles 瓶水。

如果喝掉了水瓶中的水，那么水瓶就会变成空的。

给你两个整数 numBottles 和 numExchange ，返回你 最多 可以喝到多少瓶水。

思路

这是一道模拟题。题目说了每 numExchange 个空瓶可以换一瓶水，那么我们可以模拟这个过程，每喝掉 numExchange 瓶水，就去兑换一瓶水，直到 numBottles 喝光。注意兑换的水要加回 numBottles。

复杂度

时间O(n)
空间O(1)

代码

Java实现

class Solution {
    public int numWaterBottles(int numBottles, int numExchange) {
        int count = 0;
        while (numBottles >= numExchange) {
            count += numExchange;
            numBottles -= numExchange - 1;
        }
        return count + numBottles;
    }
}