How Can We Optimize Duplicate Removal in an Array Without Using Sets?

Improving Duplicate Removal Algorithm in an Array

In this discussion, the focus will be on optimizing the implementation of a duplicate removal algorithm for an array, without utilizing high-level data structures like Set.

The provided algorithm iterates through the array twice, checking for duplicates. While this approach guarantees correctness, it can become computationally intensive for large arrays. To enhance efficiency, we can refine the algorithm as follows:

public static int[] improvedRemoveDuplicates(int[] arr) {

    int uniqueCount = 0;
    boolean[] exists = new boolean[arr.length]; // Flag to track unique elements

    for (int i = 0; i < arr.length; i++) {
        if (!exists[i]) {  // Check if element is not already unique
            arr[uniqueCount] = arr[i];
            exists[i] = true;
            uniqueCount++;
        }
    }

    int[] uniqueArray = new int[uniqueCount];
    for (int i = 0; i < uniqueCount; i++) {
        uniqueArray[i] = arr[i];
    }
    return uniqueArray;
}

In this improved algorithm, we introduce a boolean array exists to efficiently keep track of unique elements encountered in the original array. By setting exists[i] to true, we mark elements as seen and avoid subsequent comparisons.

Moreover, instead of shifting elements to the left to fill in gaps, we simply increment the count of unique elements and overwrite existing entries in the array. This optimization reduces the number of array operations significantly.

By utilizing these enhancements, the algorithm maintains correctness while significantly improving its performance, making it suitable for large arrays.

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