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Water Bottles

· Easy

LeetCode problem 1518

Initialise an ans variable to track the answer - it will be set to numBottles initially, since we are definitely drinking numBottles of water.

Then, while numBottles >= numExchange, it implies that we can still exchange our empty bottles for new ones. This means while the above inequality is true, we can simply add numBottles / numExchange to our ans (as these are the full bottles of water we are exchanging for) and then update our existing numBottles count with numBottles / numExchange + numBottles % numExchange.

code

class Solution {
public:
    int numWaterBottles(int numBottles, int numExchange) {
        int ans = numBottles;
        while (numBottles >= numExchange) {
            ans += numBottles / numExchange;
            numBottles = numBottles / numExchange + numBottles % numExchange;
        }
        return ans;
    }
};

complexity

  • Time: O(n) where n is numBottles
  • Space: O(1)

time taken

  • 2 minutes and 2 seconds