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How to Solve Random Pick with Blacklist Problem
Master the Random Pick with Blacklist 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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LeetCode ProblemRandom Pick with Blacklist
You are given an integer n and an array of unique integers blacklist. Design an algorithm to pick a random integer in the range [0, n - 1] that is not in blacklist. Any integer that is in the mentioned range and not in blacklist should be equally likely to be returned. Optimize your algorithm such that it minimizes the number of calls to the built-in random function of your language. Implement the Solution class:
ArrayHash TableMathBinary SearchSortingRandomized
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Problem Breakdown
Understanding the Random Pick with Blacklist Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
You are given an integer n and an array of unique integers blacklist. Design an algorithm to pick a random integer in the range [0, n - 1] that is not in blacklist. Any integer that is in the mentioned range and not in blacklist should be equally likely to be returned. Optimize your algorithm such that it minimizes the number of calls to the built-in random function of your language. Implement the Solution class:
HardProblem #710
LeetCodeRandom Pick with Blacklist
Related Topics
ArrayHash TableMathBinary SearchSortingRandomized
How Phantom Code Helps
Get real-time assistance for Random Pick with Blacklist problems during coding interviews. Phantom Code provides instant solutions and explanations.
Examples
# Example 1
Input
—
Output
—
Constraints
1 <= n <= 109
0 <= blacklist.length <= min(105, n - 1)
0 <= blacklist[i] < n
All the values of blacklist are unique.
At most 2 * 104 calls will be made to pick.
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Solve Random Pick with Blacklist — You are given an integer n and an array of unique integers blacklist. Design an ...
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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Frequently Asked Questions
Common questions about solving Random Pick with Blacklist and using Phantom Code during coding interviews.
How does Phantom Code help me solve coding problems like Random Pick with Blacklist 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 Random Pick with Blacklist?
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 Random Pick with Blacklist?
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 Random Pick with Blacklist 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 Random Pick with Blacklist 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 Random Pick with Blacklist 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 Random Pick with Blacklist 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 Random Pick with Blacklist 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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