Used by thousands of developers who passed their interviews
How to Solve Reorder Routes to Make All Paths Lead to the City Zero Problem
Master the Reorder Routes to Make All Paths Lead to the City Zero 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#1466
LeetCode ProblemReorder Routes to Make All Paths Lead to the City Zero
There are n cities numbered from 0 to n - 1 and n - 1 roads such that there is only one way to travel between two different cities (this network form a tree). Last year, The ministry of transport decided to orient the roads in one direction because they are too narrow. Roads are represented by connections where connections[i] = [ai, bi] represents a road from city ai to city bi. This year, there will be a big event in the capital (city 0), and many people want to travel to this city. Your task consists of reorienting some roads such that each city can visit the city 0. Return the minimum number of edges changed. It's guaranteed that each city can reach city 0 after reorder.
PhantomCodeAI will help you solve this problem in real-time during your interview
Get instant solutions, explanations, and code generation
Problem Breakdown
Understanding the Reorder Routes to Make All Paths Lead to the City Zero Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
There are n cities numbered from 0 to n - 1 and n - 1 roads such that there is only one way to travel between two different cities (this network form a tree). Last year, The ministry of transport decided to orient the roads in one direction because they are too narrow. Roads are represented by connections where connections[i] = [ai, bi] represents a road from city ai to city bi. This year, there will be a big event in the capital (city 0), and many people want to travel to this city. Your task consists of reorienting some roads such that each city can visit the city 0. Return the minimum number of edges changed. It's guaranteed that each city can reach city 0 after reorder.
MediumProblem #1466
LeetCodeReorder Routes to Make All Paths Lead to the City Zero
Related Topics
How PhantomCodeAI Helps
Get real-time assistance for Reorder Routes to Make All Paths Lead to the City Zero problems during coding interviews. PhantomCodeAI provides instant solutions and explanations.
Examples
# Example 1
Input
n = 6, connections = [[0,1],[1,3],[2,3],[4,0],[4,5]]
Output
3
# Example 2
Input
n = 5, connections = [[1,0],[1,2],[3,2],[3,4]]
Output
2
# Example 3
Input
n = 3, connections = [[1,0],[2,0]]
Output
0
Constraints
2 <= n <= 5 * 104
connections.length == n - 1
connections[i].length == 2
0 <= ai, bi <= n - 1
ai != bi
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 Reorder Routes to Make All Paths Lead to the City Zero — There are n cities numbered from 0 to n - 1 and n - 1 roads such that there is o...
Here's the optimal approach using Depth-First Search:
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 Reorder Routes to Make All Paths Lead to the City Zero 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 Reorder Routes to Make All Paths Lead to the City Zero.
20+ Stealth Features. Zero Detection Cases.
The only AI interview tool with an undetectable desktop overlay, real-time audio listening, and personalized AI responses.