希尔排序--(ShellSort)

public class TestShellSort {

    public static void shellSort(int[] arr) {

        for (int gap = arr.length >> 1; gap > 0; gap >>= 1) {
            for (int i = gap; i < arr.length; i++) {
                for (int j = i; j > gap - 1; j -= gap) {
                    if (arr[j] < arr[j - gap]) {
                        swap(arr, j, j - gap);
                    }
                }
            }
        }
    }

    public static void swap(int[] arr, int i, int minIndex) {
        int tmp = arr[i];
        arr[i] = arr[minIndex];
        arr[minIndex] = tmp;
    }
}

进行一个优化

public class TestShellSort {

    public static void shellSort(int[] arr) {
        //使用 knuth 序列
        int h = 1;
        while (h <= arr.length) {
            h = h * 3 + 1;
        }
        for (int gap = h; gap > 0; gap = (gap - 1) / 3) {
            for (int i = gap; i < arr.length; i++) {
                for (int j = i; j > gap - 1; j -= gap) {
                    if (arr[j] < arr[j - gap]) {
                        swap(arr, j, j - gap);
                    }
                }
            }
        }
    }

    public static void swap(int[] arr, int i, int minIndex) {
        int tmp = arr[i];
        arr[i] = arr[minIndex];
        arr[minIndex] = tmp;
    }
}