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LeetCode solutions

2317. Count Collisions on a Road

My accepted Python solution to LeetCode problem 2317, Count Collisions on a Road, running in 54ms.

  • Difficulty: Medium
  • Python
  • Runtime 54ms
  • Memory 17.9MB

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 54ms, memory 17.9MB, accepted 2025-12-30.

python
class Solution:
    def countCollisions(self, directions: str) -> int:
        # Cars going left at the start never collide
        # Cars going right at the end never collide
        # All other moving cars will eventually collide
        
        # Strip L's from left and R's from right
        directions = directions.lstrip('L').rstrip('R')
        
        # Count remaining moving cars (L's and R's)
        collisions = 0
        for c in directions:
            if c != 'S':
                collisions += 1
        
        return collisions

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