How do you sort an array in wave form?
This problem evaluates your sorting intuition and ability to rearrange elements based on specific adjacency constraints.
Why Interviewers Ask This
It tests your ability to follow specific patterns and constraints in data manipulation. Interviewers look for efficient sorting strategies versus simple swaps. It also checks if you understand the definition of a wave array (a[i] >= a[i+1] <= a[i+2]).
How to Answer This Question
Sort the array first, then swap adjacent pairs. Alternatively, iterate and swap if the condition isn't met. Explain the sorted approach for simplicity. Discuss the O(n log n) vs O(n) approaches. Provide a clear example to illustrate the wave pattern.
Key Points to Cover
- Sorting prerequisite
- Adjacent swapping logic
- Wave pattern definition
- Time complexity analysis
Sample Answer
First, sort the array in ascending order. Then, iterate through the array with a step of 2 and swap each element with its neighbor. This ensures arr[0] >= arr[1] <= arr[2] >= arr[3]. This approach takes O(n log n) due to sorting but is straightforward to implement.
Common Mistakes to Avoid
- Swapping without sorting
- Incorrect index stepping
- Failing to handle odd-length arrays
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