Watering Plants II

Problem Description

Alice and Bob want to water n plants in their garden, each requiring a specific amount of water. Alice waters the plants from left to right, while Bob waters from right to left, both starting with full watering cans. They refill their cans when needed, and if they reach the same plant, the one with more water waters the plant. The task is to determine the number of times they have to refill their cans to water all the plants.

Key Insights

• Alice and Bob water the plants simultaneously but from opposite ends.
• They can refill their cans whenever they don't have enough water for the next plant.
• In case of a tie while reaching the same plant, Alice gets priority.
• The problem can be solved using a two-pointer approach to simulate the watering process.

Space and Time Complexity

Time Complexity: O(n) - We process each plant once. Space Complexity: O(1) - We use a constant amount of space.

Solution

The solution involves using two pointers, one for Alice starting at the leftmost plant and another for Bob starting at the rightmost plant. We simulate the watering process as follows:

1. Initialize Alice's and Bob's water amounts with their respective capacities.
2. Use a loop to continue until both pointers meet.
3. Depending on the current water levels and the plant requirements, either Alice or Bob will water the plant. If they need to refill, we increment the refill count.
4. Adjust the water levels after each watering action.

Code Solutions