2079. Watering Plants

MediumLeetCode

You want to water n plants in your garden with a watering can. 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. There is a river at x = -1 that you can refill your watering can at.

Each plant needs a specific amount of water. You will water the plants in the following way:

• Water the plants in order from left to right.
• After watering the current plant, if you do not have enough water to completely water the next plant, return to the river to fully refill the watering can.
• You cannot refill the watering can early.
• You are initially at the river (i.e., x = -1). It takes one step to move one unit on the x-axis.

Given a 0-indexed integer array plants of n integers, where plants[i] is the amount of water the ith plant needs, and an integer capacity representing the watering can capacity, return the number of steps needed to water all the plants.

Example 1

Input: plants = [2,2,3,3], capacity = 5

Output: 14

Explanation: Start at the river with a full watering can:

• Walk to plant 0 (1 step) and water it. Watering can has 3 units of water.
• Walk to plant 1 (1 step) and water it. Watering can has 1 unit of water.
• Since you cannot completely water plant 2, walk back to the river to refill (2 steps).
• Walk to plant 2 (3 steps) and water it. Watering can has 2 units of water.
• Since you cannot completely water plant 3, walk back to the river to refill (3 steps).
• Walk to plant 3 (4 steps) and water it. Steps needed = 1 + 1 + 2 + 3 + 3 + 4 = 14.

Example 2

Input: plants = [1,1,1,4,2,3], capacity = 4

Output: 30

Explanation: Start at the river with a full watering can:

• Water plants 0, 1, and 2 (3 steps). Return to river (3 steps).
• Water plant 3 (4 steps). Return to river (4 steps).
• Water plant 4 (5 steps). Return to river (5 steps).
• Water plant 5 (6 steps). Steps needed = 3 + 3 + 4 + 4 + 5 + 5 + 6 = 30.

Example 3

Input: plants = [7,7,7,7,7,7,7], capacity = 8

Output: 49

Explanation: You have to refill before watering each plant. Steps needed = 1 + 1 + 2 + 2 + 3 + 3 + 4 + 4 + 5 + 5 + 6 + 6 + 7 = 49.

Constraints

• n == plants.length
• 1 <= n <= 1000
• 1 <= plants[i] <= 10^6
• max(plants[i]) <= capacity <= 10^9

How to solve the problem

class Solution:
    def wateringPlants(self, plants: List[int], capacity: int) -> int:
        maxCapacity = capacity
        counter = 0
        for i in range(len(plants)):
            if capacity >= plants[i]:
                capacity -= plants[i]
                counter += 1
            else:
                capacity = maxCapacity - plants[i]
                counter += i * 2 + 1

        return counter

Complexity

• Time complexity: O(n), Space complexity: O(1)