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:
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); } }
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); }