Maximum Enemy Forts That Can Be Captured — LeetCode 2511 Python Solution

The problem

You are given a 0-indexed integer array forts of length n representing the positions of several forts. forts[i] can be -1, 0, or 1 where: -1 represents there is no fort at the ith position.

Example

Input

forts = [1,0,0,-1,0,0,0,0,1]

Output

4

Explanation

- Moving the army from position 0 to position 3 captures 2 enemy forts, at 1 and 2.

Python solution

class Solution:
    def captureForts(self, forts: List[int]) -> int:
        n = len(forts)
        i = ans = 0
        while i < n:
            j = i + 1
            if forts[i]:
                while j < n and forts[j] == 0:
                    j += 1
                if j < n and forts[i] + forts[j] == 0:
                    ans = max(ans, j - i - 1)
            i = j
        return ans

Complexity

Pattern: Two Pointers

Use the order already in the input to discard half the search space at every step. LeetCode 2511. Maximum Enemy Forts That Can Be Captured 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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