Greedy on array
Last updated: November 7, 2025
Quick Overview
Given an array of integers, implement a greedy algorithm to find the maximum sum of non-adjacent elements. You need to return the maximum sum possible by selecting elements such that no two selected elements are adjacent in the array. The input will be an array of integers, and the output should be a single integer representing the maximum sum.
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November 7, 20251
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Given an array of integers, implement a greedy algorithm to find the maximum sum of non-adjacent elements. You need to return the maximum sum possible by selecting elements such that no two selected elements are adjacent in the array. The input will be an array of integers, and the output should be a single integer representing the maximum sum.
Coding interviews at Snapchat 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
- What happens if the input contains duplicates?
- How would your solution change if the input was sorted?
- Can you optimize the space complexity of your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
This problem can be recognized as a dynamic programming problem, which often employs a greedy approach to maximize the sum of non-adjacent elements in an array. The adjacency constraint means that if ...
Approach
- Initialize two variables:
include(to store the maximum sum including the current element) andexclude(to store the maximum sum excluding the current element). Set both to 0 initially. - ...
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