README.md

1518. Water Bottles

Given numBottles full water bottles, you can exchange numExchange empty water bottles for one full water bottle.

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

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.

Example 3:

Input: numBottles = 5, numExchange = 5
Output: 6

Example 4:

Input: numBottles = 2, numExchange = 3
Output: 2

Constraints:

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

Solutions (Ruby)

1. Greedy

# @param {Integer} num_bottles
# @param {Integer} num_exchange
# @return {Integer}
def num_water_bottles(num_bottles, num_exchange)
    ret = num_empty = num_bottles

    while num_empty >= num_exchange
        ret += num_empty / num_exchange
        num_empty = num_empty % num_exchange + num_empty / num_exchange
    end

    return ret
end

Solutions (Rust)

1. Greedy

impl Solution {
    pub fn num_water_bottles(num_bottles: i32, num_exchange: i32) -> i32 {
        let mut num_empty = num_bottles;
        let mut ret = num_bottles;

        while num_empty >= num_exchange {
            ret += num_empty / num_exchange;
            num_empty = num_empty % num_exchange + num_empty / num_exchange;
        }

        ret
    }
}