实例
void shell_sort(int arr[], int len) {
int gap, i, j; int temp; for (gap = len >> 1; gap > 0; gap = gap >> 1)
for (i = gap; i < len; i++) {
temp = arr[i]; for (j = i - gap; j >= 0 && arr[j] > temp; j -= gap)
arr[j + gap] = arr[j]; arr[j + gap] = temp; }}
归并排序
把数据分为两段，从两段中逐个选最小的元素移入新数据段的末尾。
可从上到下或从下到上进行。
过程演示：
迭代法
int min(int x, int y) {
return x < y ? x : y;}void merge_sort(int arr[], int len) {
int* a = arr; int* b = (int*) malloc(len * sizeof(int)); int seg, start; for (seg = 1; seg < len; seg += seg) {
for (start = 0; start < len; start += seg + seg) {
int low = start, mid = min(start + seg, len), high = min(start + seg + seg, len); int k = low; int start1 = low, end1 = mid; int start2 = mid, end2 = high; while (start1 < end1 && start2 < end2)
b[k++] = a[start1] < a[start2] ? a[start1++] : a[start2++]; while (start1 < end1)
b[k++] = a[start1++]; while (start2 < end2)
b[k++] = a[start2++]; }
int* temp = a; a = b; b = temp; }
if (a != arr) {
int i; for (i = 0; i < len; i++)
b[i] = a[i]; b = a; }
free(b);}
递归法
void merge_sort_recursive(int arr[], int reg[], int start, int end) {
if (start >= end)
return; int len = end - start, mid = (len >> 1) + start; int start1 = start, end1 = mid; int start2 = mid + 1, end2 = end; merge_sort_recursive(arr, reg, start1, end1); merge_sort_recursive(arr, reg, start2, end2); int k = start; while (start1 <= end1 && start2 <= end2)
reg[k++] = arr[start1] < arr[start2] ? arr[start1++] : arr[start2++]; while (start1 <= end1)
reg[k++] = arr[start1++]; while (start2 <= end2)
reg[k++] = arr[start2++]; for (k = start; k <= end; k++)
arr[k] = reg[k];}void merge_sort(int arr[], const int len) {
int reg[len]; merge_sort_recursive(arr, reg, 0, len - 1);}
快速排序
在区间中随机挑选一个元素作基准，将小于基准的元素放在基准之前，大于基准的元素放在基准之后，再分别对小数区与大数区进行排序。
过程演示：
迭代法
typedef struct _Range {
int start, end;} Range;Range new_Range(int s, int e) {
Range r; r.start = s; r.end = e; return r;}void swap(int *x, int *y) {
int t = *x;
*x = *y;
*y = t;}void quick_sort(int arr[], const int len) {
if (len <= 0)
return; // 避免len等於負值時引發段錯誤（Segment Fault）
// r[]模擬列表,p為數量,r[p++]為push,r[--p]為pop且取得元素
Range r[len]; int p = 0; r[p++] = new_Range(0, len - 1); while (p) {
Range range = r[--p]; if (range.start >= range.end)
continue; int mid = arr[(range.start + range.end) / 2]; // 選取中間點為基準點
int left = range.start, right = range.end; do
{
while (arr[left] < mid) ++left; // 檢測基準點左側是否符合要求
while (arr[right] > mid) --right; //檢測基準點右側是否符合要求
if (left <= right)
{
swap(&arr[left],&arr[right]); left++;right--; // 移動指針以繼續
}
} while (left <= right);
if (range.start < right) r[p++] = new_Range(range.start, right); if (range.end > left) r[p++] = new_Range(left, range.end); }}
递归法
void swap(int *x, int *y) {
int t = *x;
*x = *y;
*y = t;}void quick_sort_recursive(int arr[], int start, int end) {
if (start >= end)
return; int mid = arr[end]; int left = start, right = end - 1; while (left < right) {
while (arr[left] < mid && left < right)
left++; while (arr[right] >= mid && left < right)
right--; swap(&arr[left], &arr[right]); }
if (arr[left] >= arr[end])
swap(&arr[left], &arr[end]); else
left++; if (left)
quick_sort_recursive(arr, start, left - 1); quick_sort_recursive(arr, left + 1, end);}void quick_sort(int arr[], int len) {
quick_sort_recursive(arr, 0, len - 1);}
