希尔排序

步长串行	最坏情况下复杂度

void shellSort(int* a, int len) {
int i, gap = 0, j, k, tmp;
while (gap <= len) {
gap = gap * 3 + 1;
}
for (; gap > 0; gap = (gap - 1) / 3) {//步长
for (i = 0; i < gap; i++) {//插入排序
for (j = i + gap; j < len; j += gap) {
k = j - gap;
tmp = a[j];
while (k >= 0 && a[k] > tmp) {
a[k + gap] = a[k];
k -= gap;
}
a[k + gap] = tmp;
}
}
}
}

//代码优化
void shellSort(int* a, int len) {
int gap = 0, j, k, tmp;
while (gap <= len) {
gap = gap * 3 + 1;
}
for (; gap > 0; gap = (gap - 1) / 3) {
for (j = gap; j < len; j++) {
k = j - gap;
tmp = a[j];
while (k >= 0 && a[k] > tmp) {
a[k + gap] = a[k];
k -= gap;
}
a[k + gap] = tmp;
}
}
}