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How to Solve Count Collisions on a Road Problem
Master the Count Collisions on a Road LeetCode problem with undetectable real-time assistance. Get instant solutions and explanations during your coding interviews.
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Start Free for WindowsMedium#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.
StringStackSimulation
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Problem Breakdown
Understanding the Count Collisions on a Road Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
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
Related Topics
StringStackSimulation
How Phantom Code Helps
Get real-time assistance for Count Collisions on a Road problems during coding interviews. Phantom Code provides instant solutions and explanations.
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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Frequently Asked Questions
Common questions about solving Count Collisions on a Road and using Phantom Code during coding interviews.
How does Phantom Code help me solve coding problems like Count Collisions on a Road during interviews?
Phantom Code generates complete solutions instantly with proper complexity analysis, letting you focus on explaining your approach and demonstrating problem-solving skills rather than getting stuck on implementation details during high-pressure situations.
What if the interviewer asks follow-up questions or modifications to problems like Count Collisions on a Road?
Phantom Code adapts in real-time. Screenshot the modified problem or use audio mode to capture the interviewer's follow-up, and get an updated solution within seconds — including edge cases and optimizations.
Can Phantom Code help me communicate my solution for problems like Count Collisions on a Road?
Yes. Phantom Code provides step-by-step approach explanations with 3 progressive thoughts, so you can walk through your solution naturally. It also provides time and space complexity analysis to discuss trade-offs.
How does Phantom Code assist with different programming languages for Count Collisions on a Road type problems?
Phantom Code supports 11 programming languages including Python, Java, C++, JavaScript, TypeScript, Go, Rust, Ruby, Swift, Kotlin, and C#. Set your preferred language and get idiomatic solutions.
What coding mistakes does Phantom Code help me avoid during Count Collisions on a Road interviews?
Phantom Code catches common mistakes like off-by-one errors, missing edge cases, incorrect base conditions, and suboptimal approaches. It provides clean, well-structured code that handles all edge cases.
Is Phantom Code detectable when solving problems like Count Collisions on a Road during live interviews?
No. Phantom Code runs as an invisible desktop overlay that doesn't appear in screen shares, recordings, or proctoring software. It works with Zoom, HackerRank, CodeSignal, CoderPad, and all major platforms.
How does Phantom Code help when I'm struggling with Count Collisions on a Road style questions under pressure?
The AI provides structured guidance: first the approach (what algorithm/data structure to use and why), then the implementation with clean code, and finally complexity analysis. This helps you think clearly even under pressure.
Does Phantom Code work for the coding platforms used in Count Collisions on a Road interviews?
Yes. Phantom Code works with all major coding platforms including LeetCode, HackerRank, CodeSignal, CoderPad, HackerEarth, and any browser-based coding environment.
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