Sortings.java

import java.util.Arrays;

public class Sortings {

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

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

    // 버블 정렬 (Bubble Sort)
    public static void bubbleSort(int[] arr) {
        int n = arr.length;
        for (int i = 0; i < n - 1; i++) {
            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;
                }
            }
        }
    }

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

    // 병합 정렬 (Merge Sort)
    public 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 j = 0; j < n2; j++) {
            R[j] = arr[mid + 1 + j];
        }

        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++;
        }
    }

    // 힙 정렬 (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 l = 2 * i + 1;
        int r = 2 * i + 2;

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

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

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

    // 배열 출력 함수
    public static void printArray(int[] arr) {
        System.out.println(Arrays.toString(arr));
    }

    public static void main(String[] args) {
        int[] arr = {5, 2, 9, 1, 5, 6};

        int[] arrCopy = Arrays.copyOf(arr, arr.length);

        // 삽입 정렬
        insertionSort(arrCopy);
        System.out.println("삽입 정렬: ");
        printArray(arrCopy);

        // 선택 정렬
        arrCopy = Arrays.copyOf(arr, arr.length);
        selectionSort(arrCopy);
        System.out.println("선택 정렬: ");
        printArray(arrCopy);

        // 버블 정렬
        arrCopy = Arrays.copyOf(arr, arr.length);
        bubbleSort(arrCopy);
        System.out.println("버블 정렬: ");
        printArray(arrCopy);

        // 퀵 정렬
        arrCopy = Arrays.copyOf(arr, arr.length);
        quickSort(arrCopy, 0, arrCopy.length - 1);
        System.out.println("퀵 정렬: ");
        printArray(arrCopy);

        // 병합 정렬
        arrCopy = Arrays.copyOf(arr, arr.length);
        mergeSort(arrCopy, 0, arrCopy.length - 1);
        System.out.println("병합 정렬: ");
        printArray(arrCopy);

        // 힙 정렬
        arrCopy = Arrays.copyOf(arr, arr.length);
        heapSort(arrCopy);
        System.out.println("힙 정렬: ");
        printArray(arrCopy);
    }
}