Watering Plants II — LeetCode 2105 Python Solution

The problem

Alice and Bob want to water n plants in their garden. The plants are arranged in a row and are labeled from 0 to n - 1 from left to right where the ith plant is located at x = i.

Example

Input

plants = [2,2,3,3], capacityA = 5, capacityB = 5

Output

1

Explanation

- Initially, Alice and Bob have 5 units of water each in their watering cans.

Python solution

class Solution:
    def minimumRefill(self, plants: List[int], capacityA: int, capacityB: int) -> int:
        a, b = capacityA, capacityB
        ans = 0
        i, j = 0, len(plants) - 1
        while i < j:
            if a < plants[i]:
                ans += 1
                a = capacityA
            a -= plants[i]
            if b < plants[j]:
                ans += 1
                b = capacityB
            b -= plants[j]
            i, j = i + 1, j - 1
        ans += i == j and max(a, b) < plants[i]
        return ans

Complexity

Pattern: Two Pointers

Use the order already in the input to discard half the search space at every step. LeetCode 2105. Watering Plants II is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Two Pointers.

The two pointers guide has the Python template for the pattern and the 201 LeetCode problems that use it.

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