经典算法

快速排序

public class QuickSort {
    public static void quickSort(int[] arr, int left, int right) {
        if (left < right) {
            int pIndex = partition(arr, left, right);
            quickSort(arr, left, pIndex - 1);
            quickSort(arr, pIndex + 1, right);
        }
    }
 
    private static int partition(int[] arr, int left, int right) {
        int pivot = arr[right]; // 选择右侧元素作为主元素
        int i = left - 1;
 
        for (int j = left; j < right; j++) {
            if (arr[j] < pivot) {
                i++;
                swap(arr, i, j);
            }
        }
 
        swap(arr, i + 1, right);
        return i + 1;
    }
 
    private static void swap(int[] arr, int i, int j) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }
 
    public static void main(String[] args) {
        int[] arr = {5, 3, 7, 1, 9, 2, 8, 4, 6};
        quickSort(arr, 0, arr.length - 1);
        System.out.println(Arrays.toString(arr));
    }
}