希尔排序（Java实现）

步长分组的插入排序

public class ShellSort {
    public static void main(String[] args) {
        int[] data = {15, 9, 7, 8, 20, -1, 4};
        shellSort(data);
    }

    private static void shellSort(int[] data) {
        int n = data.length;
        int k = n;
        int[] delta = new int[n >> 1];
        int i = 0;

        do {
            k >> 1;
            delta[i++] = k;
        } while (k > 1);

        i = 0;
        int dk;
        while ((dk = delta[i]) > 0) {//步长
            for (k = delta[i]; k < n; k++) {
                if (data[k - dk] > data[k]) {
                    int t = data[k];
                    int j;

                    for (j = k - dk; j >= 0 && data[j] > t; j -= dk) {
                        data[j + dk] = data[j];
                    }
                    data[j + dk] = t;
                }
            }
            i++;
        }
    }
}

x >> 1 等同于 x /= 2 且位运算效率更高