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How to Solve Last Moment Before All Ants Fall Out of a Plank Problem

Master the Last Moment Before All Ants Fall Out of a Plank LeetCode problem with undetectable real-time assistance. Get instant solutions and explanations during your coding interviews.

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Medium#1503

LeetCode Problem

Last Moment Before All Ants Fall Out of a Plank

We have a wooden plank of the length n units. Some ants are walking on the plank, each ant moves with a speed of 1 unit per second. Some of the ants move to the left, the other move to the right. When two ants moving in two different directions meet at some point, they change their directions and continue moving again. Assume changing directions does not take any additional time. When an ant reaches one end of the plank at a time t, it falls out of the plank immediately. Given an integer n and two integer arrays left and right, the positions of the ants moving to the left and the right, return the moment when the last ant(s) fall out of the plank.

ArrayBrainteaserSimulation

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Problem Breakdown

Understanding the Last Moment Before All Ants Fall Out of a Plank Problem

Let's break down this LeetCode problem and understand what makes it challenging in interview settings.

Problem Statement

MediumProblem #1503

LeetCode

Last Moment Before All Ants Fall Out of a Plank

How Phantom Code Helps

Get real-time assistance for Last Moment Before All Ants Fall Out of a Plank problems during coding interviews. Phantom Code provides instant solutions and explanations.

Examples

# Example 1

Input

n = 4, left = [4,3], right = [0,1]

Output

# Example 2

Input

n = 7, left = [], right = [0,1,2,3,4,5,6,7]

Output

# Example 3

Input

n = 7, left = [0,1,2,3,4,5,6,7], right = []

Output

Constraints

1 <= n <= 104

0 <= left.length <= n + 1

0 <= left[i] <= n

0 <= right.length <= n + 1

0 <= right[i] <= n

1 <= left.length + right.length <= n + 1

All values of left and right are unique, and each value can appear only in one of the two arrays.

How Phantom Code Helps with LeetCode Problems

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Solve Last Moment Before All Ants Fall Out of a Plank — We have a wooden plank of the length n units. Some ants are walking on the plank...

Here's the optimal approach using Array:

def solve(input):

# Optimal O(n) solution

return result

Time: O(n) | Space: O(n)

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Undetectability Checklist

Run compatibility test before interviews

Use recommended Zoom version settings

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Verify native desktop architecture

Test with screen recording software

Platform Compatibility

Zoom

Supported

Google Meet

Supported

HackerRank

Supported

CodeSignal

Supported

CoderPad

Supported

Teams

Supported

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Undetectability and technical details

Our native desktop architecture avoids common detection vectors used by browser extensions. We provide a clear checklist so you can run basic checks and confirm the app will be invisible.

Platform compatibility and limitations

We work with Zoom, HackerRank, CodeSignal, CoderPad and other web-based platforms. Check the compatibility note and request a browser link if a specific desktop app is unsupported.

Frequently Asked Questions

Common questions about solving Last Moment Before All Ants Fall Out of a Plank and using Phantom Code during coding interviews.

How does Phantom Code help me solve coding problems like Last Moment Before All Ants Fall Out of a Plank 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 Last Moment Before All Ants Fall Out of a Plank?

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 Last Moment Before All Ants Fall Out of a Plank?

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 Last Moment Before All Ants Fall Out of a Plank 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 Last Moment Before All Ants Fall Out of a Plank 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 Last Moment Before All Ants Fall Out of a Plank 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 Last Moment Before All Ants Fall Out of a Plank 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 Last Moment Before All Ants Fall Out of a Plank 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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