Implementing Radix Sort in Java from Scratch

Radix Sort is a non-comparative sorting algorithm that processes integer keys by sorting numbers digit by digit, starting from the least significant digit (LSD) to the most significant digit (MSD). It's a linear time sorting algorithm, making it efficient for large datasets. Let's dive deep into understanding Radix Sort and its implementation in Java.

How Radix Sort Works

Radix Sort operates by distributing elements into buckets according to their individual digits. Here's a step-by-step breakdown:

1. Initialization: Create 10 buckets, one for each digit (0 to 9).
2. Distribution: Starting from the least significant digit, place each number in the corresponding bucket.
3. Collection: Gather numbers from the buckets, preserving the order they were added.
4. Repetition: Repeat the distribution and collection steps for the next significant digit.

This process continues until all digits in the longest number have been processed.

Java Implementation of Radix Sort

Setting Up the Environment

Before diving into the code, ensure you have the Java Development Kit (JDK) installed. This guide assumes familiarity with Java's basic syntax and structure.

The Radix Sort Algorithm

Here's a detailed Java implementation of the Radix Sort algorithm:

public class RadixSort {

    // Utility function to get the maximum value in the array
    public static int getMax(int[] arr, int n) {
        int max = arr[0];
        for (int i = 1; i < n; i++) {
            if (arr[i] > max) {
                max = arr[i];
            }
        }
        return max;
    }

    // Main Radix Sort function
    public static void radixSort(int[] arr, int n) {
        int max = getMax(arr, n);

        // Do counting sort for every digit
        for (int exp = 1; max / exp > 0; exp *= 10) {
            countingSortByDigit(arr, n, exp);
        }
    }

    // Counting Sort function to sort arr[] based on significant places
    private static void countingSortByDigit(int[] arr, int n, int exp) {
        int[] output = new int[n];
        int[] count = new int[10];
        Arrays.fill(count, 0);

        // Store count of occurrences in count[]
        for (int i = 0; i < n; i++) {
            count[(arr[i] / exp) % 10]++;
        }

        // Change count[i] so that it contains the actual position of this digit in output[]
        for (int i = 1; i < 10; i++) {
            count[i] += count[i - 1];
        }

        // Build the output array
        for (int i = n - 1; i >= 0; i--) {
            output[count[(arr[i] / exp) % 10] - 1] = arr[i];
            count[(arr[i] / exp) % 10]--;
        }

        // Copy the output array to arr[] so that arr[] contains sorted numbers based on this digit
        for (int i = 0; i < n; i++) {
            arr[i] = output[i];
        }
    }

    public static void main(String[] args) {
        int[] arr = {170, 45, 75, 90, 802, 24, 2, 66};
        int n = arr.length;
        radixSort(arr, n);
        System.out.println("Sorted array: " + Arrays.toString(arr));
    }
}

Advantages of Radix Sort

Radix Sort offers several benefits:

• Efficiency: It's a linear time sorting algorithm, especially beneficial for large datasets.
• Stability: It maintains the relative order of equal elements, ensuring consistent results.
• Flexibility: While primarily used for integers, it can be adapted for strings or other data types.

Wrapping Up

Radix Sort is a powerful and efficient sorting algorithm, especially for datasets with large numbers. Its method of sorting digit by digit ensures accuracy and efficiency. With the provided Java implementation, software engineers and developers can seamlessly integrate it into their projects, ensuring sorted data in linear time.