Leetcode #2086: Minimum Number of Food Buckets to Feed the Hamsters
In this guide, we solve Leetcode #2086 Minimum Number of Food Buckets to Feed the Hamsters in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
You are given a 0-indexed string hamsters where hamsters[i] is either: 'H' indicating that there is a hamster at index i, or '.' indicating that index i is empty. You will add some number of food buckets at the empty indices in order to feed the hamsters.
Quick Facts
- Difficulty: Medium
- Premium: No
- Tags: Greedy, String, Dynamic Programming
Intuition
The problem breaks into overlapping subproblems, so caching results prevents exponential repetition.
A carefully chosen DP state captures exactly what we need to build the final answer.
Approach
Define the DP state and recurrence, then compute states in the correct order.
Optionally compress space once the recurrence is clear.
Steps:
- Choose a DP state definition.
- Write the recurrence and base cases.
- Compute states in the correct order.
Example
Input: hamsters = "H..H"
Output: 2
Explanation: We place two food buckets at indices 1 and 2.
It can be shown that if we place only one food bucket, one of the hamsters will not be fed.
Python Solution
class Solution:
def minimumBuckets(self, street: str) -> int:
ans = 0
i, n = 0, len(street)
while i < n:
if street[i] == 'H':
if i + 1 < n and street[i + 1] == '.':
i += 2
ans += 1
elif i and street[i - 1] == '.':
ans += 1
else:
return -1
i += 1
return ans
Complexity
The time complexity is O(n·m) (typical). The space complexity is O(n·m) or optimized.
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.