快速排序

参考

public class QuickSort {

    public static int[][] sortCases = {
            {1},
            {1, 2},
            {2, 1},
            {1, 2, 3},
            {1, 3, 2},
            {2, 1, 3},
            {2, 3, 1},
            {3, 1, 2},
            {3, 2, 1},
            {2, 4, 3, 3, 5, 6, 4, 6, 5, 2, 1},
            {1, 2, 2, 3, 1, 1, 1, 4, 3, 3, 3, 5, 5, 5, 5},
            {3, 3, 5, 4, 2, 1, 2, 3, 3, 5, 6, 7, 8, 7, 6, 7, 4, 2, 3, 4, 1, 5, 3, 4, 4, 5, 2, 0},
    };

    private static void quickSort(int[] array, int start, int end) {
        if (start < end) {
            int mid = partition(array, start, end);
            quickSort(array, start, mid - 1);
            quickSort(array, mid + 1, end);
        }
    }

    private static int partition(int[] src, int start, int end) {
        int target = src[start];
        while (start < end) {
            while (start < end && src[end] >= target) {
                end--;
            }
            src[start] = src[end];
            while (start < end && src[start] <= target) {
                start++;
            }
            src[end] = src[start];
        }
        // 此时 start == end
        src[start] = target;
        return start;
    }

    public static void main(String[] args) {
        testSort();
    }

    private static void testSort() {
        for (int[] each : sortCases) {
            quickSort(each, 0, each.length - 1);
            checkArray(each);
        }
    }

    private static void checkArray(int[] arr) {
        for (int i = 0; i < arr.length; i++) {
            if (i != 0 && arr[i - 1] > arr[i]) {
                System.out.println("error");
            }
            System.out.print(arr[i] + " ");
        }
        System.out.println();
        System.out.println("Correct!");
    }
}