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How to Solve Count Collisions on a Road Problem
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Medium#2211
LeetCode ProblemCount Collisions on a Road
There are n cars on an infinitely long road. The cars are numbered from 0 to n - 1 from left to right and each car is present at a unique point. You are given a 0-indexed string directions of length n. directions[i] can be either 'L', 'R', or 'S' denoting whether the ith car is moving towards the left, towards the right, or staying at its current point respectively. Each moving car has the same speed. The number of collisions can be calculated as follows: After a collision, the cars involved can no longer move and will stay at the point where they collided. Other than that, cars cannot change their state or direction of motion. Return the total number of collisions that will happen on the road.
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Problem Breakdown
Understanding the Count Collisions on a Road Problem
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Problem Statement
There are n cars on an infinitely long road. The cars are numbered from 0 to n - 1 from left to right and each car is present at a unique point. You are given a 0-indexed string directions of length n. directions[i] can be either 'L', 'R', or 'S' denoting whether the ith car is moving towards the left, towards the right, or staying at its current point respectively. Each moving car has the same speed. The number of collisions can be calculated as follows: After a collision, the cars involved can no longer move and will stay at the point where they collided. Other than that, cars cannot change their state or direction of motion. Return the total number of collisions that will happen on the road.
MediumProblem #2211
LeetCodeCount Collisions on a Road
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Examples
# Example 1
Input
directions = "RLRSLL"
Output
5
# Example 2
Input
directions = "LLRR"
Output
0
Constraints
1 <= directions.length <= 105
directions[i] is either 'L', 'R', or 'S'.
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Solve Count Collisions on a Road — There are n cars on an infinitely long road. The cars are numbered from 0 to n -...
Here's the optimal approach using String:
def solve(input):
# Optimal O(n) solution
return result
Time: O(n) | Space: O(n)
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