Validate array complete
Last updated: January 5, 2026
Quick Overview
Given an array of integers, write a function to determine if the array is complete, meaning that every element from 1 to n (where n is the length of the array) appears exactly once. The function should return true if the array is complete and false otherwise.
Citadel
January 5, 20269
10
1,824 solved
Given an array of integers, write a function to determine if the array is complete, meaning that every element from 1 to n (where n is the length of the array) appears exactly once. The function should return true if the array is complete and false otherwise.
Coding interviews at Citadel focus on problem-solving approach as much as the final solution. The interviewer wants to see you break down the problem, consider edge cases, and optimize iteratively. Communication throughout the process is key.
What the Interviewer Expects
- Recognize the underlying problem pattern (sliding window, two pointers, BFS/DFS, etc.)
- Discuss multiple approaches and trade-offs before coding
- Implement an optimal solution with clean, production-quality code
- Handle all edge cases including boundary conditions and invalid input
- Optimize both time and space complexity with clear justification
- Test your solution systematically with well-chosen examples
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
- How would your solution change if the input was sorted?
- How would you modify your solution to handle streaming input?
- What if the input doesn't fit in memory?
- How would you parallelize this solution?
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Problem Analysis
The problem requires us to validate whether an array of integers contains every number from 1 to n exactly once, where n is the length of the array. This can be efficiently tackled using a frequency c...
Approach
- Initialize a Set: Create an empty set to keep track of the numbers we encounter in the array.
- Iterate through the Array: Loop through each number in the array:
- Check if the number i...
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