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LeetCode solutions

2251. Number of Ways to Divide a Long Corridor

My accepted Python solution to LeetCode problem 2251, Number of Ways to Divide a Long Corridor, running in 223ms.

  • Difficulty: Hard
  • Python
  • Runtime 223ms
  • Memory 21.5MB

Read the problem on LeetCode View on GitHub

The problem statement is LeetCode’s and stays on their site. What follows is my accepted solution.

Python

Accepted on LeetCode — runtime 223ms, memory 21.5MB, accepted 2026-01-01.

python
class Solution:
    def numberOfWays(self, corridor: str) -> int:
        MOD = 10**9 + 7
        
        # Find positions of all seats
        seats = [i for i, c in enumerate(corridor) if c == 'S']
        
        # Need even number of seats >= 2
        if len(seats) < 2 or len(seats) % 2 != 0:
            return 0
        
        result = 1
        # For each pair of seats, count plants between pairs
        for i in range(2, len(seats), 2):
            # Gap between seat i-1 and seat i
            gap = seats[i] - seats[i-1]
            result = (result * gap) % MOD
        
        return result

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