Detect permutation in array
Last updated: October 28, 2025
Quick Overview
Given two arrays, determine if one array is a permutation of the other. The input consists of two arrays of integers, and the output should be a boolean value indicating whether the second array can be formed by rearranging the elements of the first array.
Jane Street
October 28, 202550
14
3,674 solved
Given two arrays, determine if one array is a permutation of the other. The input consists of two arrays of integers, and the output should be a boolean value indicating whether the second array can be formed by rearranging the elements of the first array.
This coding problem is frequently asked during Phone Screen at Jane Street. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Jane Street expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Identify the correct data structure and algorithm for the problem
- Write clean, bug-free code with proper variable naming
- Analyze time and space complexity correctly
- Handle basic edge cases (empty input, single element)
- Communicate your thought process while coding
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- What if the input doesn't fit in memory?
- How would your solution change if the input was sorted?
- What is the worst-case input for your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
To determine if one array is a permutation of another, we can use the frequency counting pattern. This applies here because a permutation means that both arrays must contain the same elements in t...
Approach
- Check Lengths: First, check if both arrays have the same length. If not, return false immediately.
- Frequency Count: Use a dictionary (hashmap) to count occurrences of each integer in th...
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