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How to Solve First Day Where You Have Been in All the Rooms Problem
Master the First Day Where You Have Been in All the Rooms LeetCode problem with undetectable real-time assistance. Get instant solutions and explanations during your coding interviews.
Phantom Code generates complete solutions and debugging hints that you can use while explaining your approach, so you stay calm and in control.
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Start Free for WindowsMedium#1997
LeetCode ProblemFirst Day Where You Have Been in All the Rooms
There are n rooms you need to visit, labeled from 0 to n - 1. Each day is labeled, starting from 0. You will go in and visit one room a day. Initially on day 0, you visit room 0. The order you visit the rooms for the coming days is determined by the following rules and a given 0-indexed array nextVisit of length n: Return the label of the first day where you have been in all the rooms. It can be shown that such a day exists. Since the answer may be very large, return it modulo 109 + 7.
ArrayDynamic Programming
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Problem Breakdown
Understanding the First Day Where You Have Been in All the Rooms Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
There are n rooms you need to visit, labeled from 0 to n - 1. Each day is labeled, starting from 0. You will go in and visit one room a day. Initially on day 0, you visit room 0. The order you visit the rooms for the coming days is determined by the following rules and a given 0-indexed array nextVisit of length n: Return the label of the first day where you have been in all the rooms. It can be shown that such a day exists. Since the answer may be very large, return it modulo 109 + 7.
MediumProblem #1997
LeetCodeFirst Day Where You Have Been in All the Rooms
Related Topics
ArrayDynamic Programming
How Phantom Code Helps
Get real-time assistance for First Day Where You Have Been in All the Rooms problems during coding interviews. Phantom Code provides instant solutions and explanations.
Examples
# Example 1
Input
nextVisit = [0,0]
Output
2
# Example 2
Input
nextVisit = [0,0,2]
Output
6
# Example 3
Input
nextVisit = [0,1,2,0]
Output
6
Constraints
n == nextVisit.length
2 <= n <= 105
0 <= nextVisit[i] <= i
How Phantom Code Helps with LeetCode Problems
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Solve First Day Where You Have Been in All the Rooms — There are n rooms you need to visit, labeled from 0 to n - 1. Each day is labele...
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
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Platform Compatibility
Zoom
Supported
Google Meet
Supported
HackerRank
Supported
CodeSignal
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CoderPad
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Teams
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Undetectability and technical details
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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 First Day Where You Have Been in All the Rooms and using Phantom Code during coding interviews.
How does Phantom Code help me solve coding problems like First Day Where You Have Been in All the Rooms 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 First Day Where You Have Been in All the Rooms?
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 First Day Where You Have Been in All the Rooms?
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 First Day Where You Have Been in All the Rooms 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 First Day Where You Have Been in All the Rooms 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 First Day Where You Have Been in All the Rooms 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 First Day Where You Have Been in All the Rooms 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 First Day Where You Have Been in All the Rooms 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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