Practice/Google/Remove Duplicates with Order Preservation

Remove Duplicates with Order Preservation

CodingMust

Problem

You are given an array of integers and an ordering instruction. Your task is to eliminate all duplicate values from the array while controlling the final arrangement of the unique elements.

The ordering instruction can be one of two values:

• "original": Keep the unique elements in the same order as their first appearance
• "reverse": Keep the unique elements but reverse their order after deduplication

When a value appears multiple times, only its first occurrence should be considered for position purposes.

Requirements

1. Remove all duplicate elements from the input array
2. Preserve only the first occurrence of each unique value
3. Apply the specified ordering transformation ("original" or "reverse")
4. Return a new array with the processed elements
5. Handle empty arrays appropriately

Constraints

• Array length: 0 ≤ n ≤ 10,000
• Array elements: -10^6 ≤ element ≤ 10^6
• Order parameter will be either "original" or "reverse"
• Time complexity target: O(n)
• Space complexity target: O(n)

Examples

Example 1:

Input: arr = [3, 1, 2, 1, 3, 4, 2], order = "original" Output: [3, 1, 2, 4] Explanation: We keep the first occurrence of each number (3, 1, 2, 4) and maintain their original sequence.

Example 2:

Input: arr = [3, 1, 2, 1, 3, 4, 2], order = "reverse" Output: [4, 2, 1, 3] Explanation: First we get unique elements [3, 1, 2, 4], then reverse to get [4, 2, 1, 3].

Example 3:

Input: arr = [5, 5, 5], order = "original" Output: [5] Explanation: All elements are duplicates, only one 5 remains.

Example 4:

Input: arr = [], order = "reverse" Output: [] Explanation: Empty array remains empty regardless of ordering.