Used by thousands of developers who passed their interviews
How to Solve Where Will the Ball Fall Problem
Master the Where Will the Ball Fall LeetCode problem with undetectable real-time assistance. Get instant solutions and explanations during your coding interviews.
PhantomCodeAI generates complete solutions and debugging hints that you can use while explaining your approach, so you stay calm and in control.
undetectable
real-time
works on major platforms
Medium#1706
LeetCode ProblemWhere Will the Ball Fall
You have a 2-D grid of size m x n representing a box, and you have n balls. The box is open on the top and bottom sides. Each cell in the box has a diagonal board spanning two corners of the cell that can redirect a ball to the right or to the left. We drop one ball at the top of each column of the box. Each ball can get stuck in the box or fall out of the bottom. A ball gets stuck if it hits a "V" shaped pattern between two boards or if a board redirects the ball into either wall of the box. Return an array answer of size n where answer[i] is the column that the ball falls out of at the bottom after dropping the ball from the ith column at the top, or -1 if the ball gets stuck in the box.
PhantomCodeAI will help you solve this problem in real-time during your interview
Get instant solutions, explanations, and code generation
Problem Breakdown
Understanding the Where Will the Ball Fall Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
You have a 2-D grid of size m x n representing a box, and you have n balls. The box is open on the top and bottom sides. Each cell in the box has a diagonal board spanning two corners of the cell that can redirect a ball to the right or to the left. We drop one ball at the top of each column of the box. Each ball can get stuck in the box or fall out of the bottom. A ball gets stuck if it hits a "V" shaped pattern between two boards or if a board redirects the ball into either wall of the box. Return an array answer of size n where answer[i] is the column that the ball falls out of at the bottom after dropping the ball from the ith column at the top, or -1 if the ball gets stuck in the box.
MediumProblem #1706
LeetCodeWhere Will the Ball Fall
Related Topics
How PhantomCodeAI Helps
Get real-time assistance for Where Will the Ball Fall problems during coding interviews. PhantomCodeAI provides instant solutions and explanations.
Examples
# Example 1
Input
grid = [[1,1,1,-1,-1],[1,1,1,-1,-1],[-1,-1,-1,1,1],[1,1,1,1,-1],[-1,-1,-1,-1,-1]]
Output
[1,-1,-1,-1,-1]
# Example 2
Input
grid = [[-1]]
Output
[-1]
# Example 3
Input
grid = [[1,1,1,1,1,1],[-1,-1,-1,-1,-1,-1],[1,1,1,1,1,1],[-1,-1,-1,-1,-1,-1]]
Output
[0,1,2,3,4,-1]
Constraints
m == grid.length
n == grid[i].length
1 <= m, n <= 100
grid[i][j] is 1 or -1.
How PhantomCodeAI Helps with LeetCode Problems
Reinforce undetectability, platform compatibility, and real-time assistance to remove any doubt.
1000+
developers use PhantomCodeAI
and growing every day
95%
success rate
of users pass their interviews
100%
undetectable
native desktop architecture
Real-time
assistance
instant solutions during interviews
See PhantomCodeAI in Action
Watch how PhantomCodeAI helps solve LeetCode problems during live interviews
Start Interview
⌘I
Online Round
⌘O
Hide⌘B
Interview
Listening
Think
Solve Where Will the Ball Fall — You have a 2-D grid of size m x n representing a box, and you have n balls. The ...
Here's the optimal approach using Array:
def solve(input):
# Optimal O(n) solution
return result
Time: O(n) | Space: O(n)
Start Over ⌘G
Think & Crack ⌘↵
Undetectability Checklist
Run compatibility test before interviews
Use recommended Zoom version settings
Enable advanced screen capture options
Verify native desktop architecture
Test with screen recording software
Platform Compatibility
Zoom
Supported
Google Meet
Supported
HackerRank
Supported
CodeSignal
Supported
CoderPad
Supported
Teams
Supported
User results and traction
Thousands of developers use PhantomCodeAI. Social proof signals that this approach helps real candidates land offers across a range of companies.
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 Where Will the Ball Fall and using PhantomCodeAI during coding interviews.
How does PhantomCodeAI help with LeetCode problems during a coding interview?
PhantomCodeAI reads the problem from a screenshot or listens to it via audio, then generates a complete solution with a step-by-step approach and time/space complexity, so you can focus on explaining your reasoning rather than getting stuck on implementation.
Which programming languages does PhantomCodeAI support?
11 languages including Python, Java, C++, JavaScript, TypeScript, Go, Rust, Ruby, Swift, Kotlin, and C#. Set a preferred language to get idiomatic solutions.
Does PhantomCodeAI work with HackerRank, CodeSignal, and CoderPad?
Yes — it works alongside LeetCode, HackerRank, CodeSignal, CoderPad, and HackerEarth, plus any browser-based coding environment.
Can PhantomCodeAI handle follow-up questions and modifications?
Yes. Capture the modified problem by screenshot or audio and get an updated solution within seconds, including new edge cases and optimizations.
Is PhantomCodeAI detectable during live interviews?
PhantomCodeAI runs as a native desktop overlay that does not appear in screen shares, recordings, or proctoring software, and works with Zoom, Google Meet, Microsoft Teams, and major coding platforms.
Should I still practice these problems on my own first?
Yes. The most durable preparation is solving problems unaided first, then using AI afterward to review your approach, complexity, and missed edge cases — use it to debrief and learn, not to skip the reps.
Related LeetCode Problems
Practice more problems similar to Where Will the Ball Fall.
20+ Stealth Features. Zero Detection Cases.
The only AI interview tool with an undetectable desktop overlay, real-time audio listening, and personalized AI responses.