SortingAlgos.java

import java.util.Arrays;
import java.util.Scanner;

public class SortingProgram {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        // Input array from the user
        System.out.print("Enter the number of elements in the array: ");
        int n = input.nextInt();
        int[] arr = new int[n];

        System.out.println("Enter the elements of the array:");
        for (int i = 0; i < n; i++) {
            arr[i] = input.nextInt();
        }

        // Choose a sorting algorithm
        System.out.println("\nChoose a sorting algorithm (1-10):");
        System.out.println("1- Selection sort");
        System.out.println("2- Bubble sort");
        System.out.println("3- Insertion sort");
        System.out.println("4- Merge sort");
        System.out.println("5- Quick sort");
        System.out.println("6- Heap sort");
        System.out.println("7- Counting sort");
        System.out.println("8- Radix sort");
        System.out.println("9- Bucket Sort");
        System.out.println("10- Shell Sort");
        System.out.print("Enter your choice: ");
        int choice = input.nextInt();

        switch (choice) {
            case 1:
                selectionSort(arr);
                break;
            case 2:
                bubbleSort(arr);
                break;
            case 3:
                insertionSort(arr);
                break;
            case 4:
                mergeSort(arr);
                break;
            case 5:
                quickSort(arr, 0, n - 1);
                break;
            case 6:
                heapSort(arr);
                break;
            case 7:
                countingSort(arr);
                break;
            case 8:
                radixSort(arr);
                break;
            case 9:
                bucketSort(arr);
                break;
            case 10:
                shellSort(arr);
                break;
            default:
                System.out.println("Invalid choice. No sorting performed.");
        }

        // Print the sorted array
        System.out.println("Sorted array: " + Arrays.toString(arr));
    }

    // Selection Sort
    public static void selectionSort(int[] arr) {
        int n = arr.length;
        for (int i = 0; i < n - 1; i++) {
            int minIndex = i;
            for (int j = i + 1; j < n; j++) {
                if (arr[j] < arr[minIndex]) {
                    minIndex = j;
                }
            }
            int temp = arr[minIndex];
            arr[minIndex] = arr[i];
            arr[i] = temp;
        }
    }

    // Bubble Sort
    public static void bubbleSort(int[] arr) {
        int n = arr.length;
        boolean swapped;
        for (int i = 0; i < n - 1; i++) {
            swapped = false;
            for (int j = 0; j < n - i - 1; j++) {
                if (arr[j] > arr[j + 1]) {
                    int temp = arr[j];
                    arr[j] = arr[j + 1];
                    arr[j + 1] = temp;
                    swapped = true;
                }
            }
            if (!swapped) {
                break;
            }
        }
    }

    // Insertion Sort
    public static void insertionSort(int[] arr) {
        int n = arr.length;
        for (int i = 1; i < n; i++) {
            int key = arr[i];
            int j = i - 1;
            while (j >= 0 && arr[j] > key) {
                arr[j + 1] = arr[j];
                j--;
            }
            arr[j + 1] = key;
        }
    }

    // Merge Sort
    public static void mergeSort(int[] arr) {
        mergeSort(arr, 0, arr.length - 1);
    }

    private static void mergeSort(int[] arr, int left, int right) {
        if (left < right) {
            int mid = (left + right) / 2;
            mergeSort(arr, left, mid);
            mergeSort(arr, mid + 1, right);
            merge(arr, left, mid, right);
        }
    }

    private static void merge(int[] arr, int left, int mid, int right) {
        int n1 = mid - left + 1;
        int n2 = right - mid;
        int[] L = new int[n1];
        int[] R = new int[n2];

        for (int i = 0; i < n1; i++) {
            L[i] = arr[left + i];
        }
        for (int i = 0; i < n2; i++) {
            R[i] = arr[mid + 1 + i];
        }

        int i = 0, j = 0, k = left;
        while (i < n1 && j < n2) {
            if (L[i] <= R[j]) {
                arr[k] = L[i];
                i++;
            } else {
                arr[k] = R[j];
                j++;
            }
            k++;
        }

        while (i < n1) {
            arr[k] = L[i];
            i++;
            k++;
        }

        while (j < n2) {
            arr[k] = R[j];
            j++;
            k++;
        }
    }

    // Quick Sort
    public static void quickSort(int[] arr, int low, int high) {
        if (low < high) {
            int pivotIndex = partition(arr, low, high);
            quickSort(arr, low, pivotIndex - 1);
            quickSort(arr, pivotIndex + 1, high);
        }
    }

    private static int partition(int[] arr, int low, int high) {
        int pivot = arr[high];
        int i = low - 1;
        for (int j = low; j < high; j++) {
            if (arr[j] < pivot) {
                i++;
                int temp = arr[i];
                arr[i] = arr[j];
                arr[j] = temp;
            }
        }
        int temp = arr[i + 1];
        arr[i + 1] = arr[high];
        arr[high] = temp;
        return i + 1;
    }

    // Heap Sort
    public static void heapSort(int[] arr) {
        int n = arr.length;
        for (int i = n / 2 - 1; i >= 0; i--) {
            heapify(arr, n, i);
        }
        for (int i = n - 1; i >= 0; i--) {
            int temp = arr[0];
            arr[0] = arr[i];
            arr[i] = temp;
            heapify(arr, i, 0);
        }
    }

    private static void heapify(int[] arr, int n, int i) {
        int largest = i;
        int left = 2 * i + 1;
        int right = 2 * i + 2;

        if (left < n && arr[left] > arr[largest]) {
            largest = left;
        }
        if (right < n && arr[right] > arr[largest]) {
            largest = right;
        }

        if (largest != i) {
            int swap = arr[i];
            arr[i] = arr[largest];
            arr[largest] = swap;
            heapify(arr, n, largest);
        }
    }

    // Counting Sort
    public static void countingSort(int[] arr) {
        int n = arr.length;
        int max = Arrays.stream(arr).max().getAsInt();
        int min = Arrays.stream(arr).min().getAsInt();
        int range = max - min + 1;
        int[] count = new int[range];
        int[] output = new int[n];

        for (int i = 0; i < n; i++) {
            count[arr[i] - min]++;
        }

        for (int i = 1; i < range; i++) {
            count[i] += count[i - 1];
        }

        for (int i = n - 1; i >= 0; i--) {
            output[count[arr[i] - min] - 1] = arr[i];
            count[arr[i] - min]--;
        }

        for (int i = 0; i < n; i++) {
            arr[i] = output[i];
        }
    }

    // Radix Sort
    public static void radixSort(int[] arr) {
        int max = Arrays.stream(arr).max().getAsInt();
        for (int exp = 1; max / exp > 0; exp *= 10) {
            countingSortByDigit(arr, exp);
        }
    }

    private static void countingSortByDigit(int[] arr, int exp) {
        int n = arr.length;
        int[] output = new int[n];
        int[] count = new int[10];
        Arrays.fill(count, 0);

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

        for (int i = 1; i < 10; i++) {
            count[i] += count[i - 1];
        }

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

        for (int i = 0; i < n; i++) {
            arr[i] = output[i];
        }
    }

    // Bucket Sort
    public static void bucketSort(int[] arr) {
        int n = arr.length;
        int max = Arrays.stream(arr).max().getAsInt();
        int min = Arrays.stream(arr).min().getAsInt();
        int range = max - min + 1;

        int bucketSize = Math.min(range / n, n);
        int bucketCount = (range + bucketSize - 1) / bucketSize;

        // Create buckets
        int[][] buckets = new int[bucketCount][];
        for (int i = 0; i < bucketCount; i++) {
            buckets[i] = new int[0];
        }

        // Add elements to buckets
        for (int i = 0; i < n; i++) {
            int index = (arr[i] - min) / bucketSize;
            buckets[index] = append(buckets[index], arr[i]);
        }

        // Sort individual buckets and merge
        int index = 0;
        for (int i = 0; i < bucketCount; i++) {
            insertionSort(buckets[i]);
            for (int j = 0; j < buckets[i].length; j++) {
                arr[index++] = buckets[i][j];
            }
        }
    }

    private static int[] append(int[] arr, int value) {
        int[] result = Arrays.copyOf(arr, arr.length + 1);
        result[arr.length] = value;
        return result;
    }

    // Shell Sort
    public static void shellSort(int[] arr) {
        int n = arr.length;
        for (int gap = n / 2; gap > 0; gap /= 2) {
            for (int i = gap; i < n; i++) {
                int temp = arr[i];
                int j;
                for (j = i; j >= gap && arr[j - gap] > temp; j -= gap) {
                    arr[j] = arr[j - gap];
                }
                arr[j] = temp;
            }
        }
    }
}