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krahets
2023-04-23 14:58:03 +08:00
parent 881ece517f
commit fe8027e64a
26 changed files with 344 additions and 626 deletions
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chapter_sorting/quick_sort.md
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@@ -230,20 +230,17 @@ comments: true
```csharp title="quick_sort.cs"
/* 元素交换 */
void swap(int[] nums, int i, int j)
{
void swap(int[] nums, int i, int j) {
int tmp = nums[i];
nums[i] = nums[j];
nums[j] = tmp;
}
/* 哨兵划分 */
int partition(int[] nums, int left, int right)
{
int partition(int[] nums, int left, int right) {
// 以 nums[left] 作为基准数
int i = left, j = right;
while (i < j)
{
while (i < j) {
while (i < j && nums[j] >= nums[left])
j--; // 从右向左找首个小于基准数的元素
while (i < j && nums[i] <= nums[left])
@@ -459,8 +456,7 @@ comments: true
```csharp title="quick_sort.cs"
/* 快速排序 */
void quickSort(int[] nums, int left, int right)
{
void quickSort(int[] nums, int left, int right) {
// 子数组长度为 1 时终止递归
if (left >= right)
return;
@@ -815,8 +811,7 @@ comments: true
```csharp title="quick_sort.cs"
/* 选取三个元素的中位数 */
int medianThree(int[] nums, int left, int mid, int right)
{
int medianThree(int[] nums, int left, int mid, int right) {
// 此处使用异或运算来简化代码
// 异或规则为 0 ^ 0 = 1 ^ 1 = 0, 0 ^ 1 = 1 ^ 0 = 1
if ((nums[left] < nums[mid]) ^ (nums[left] < nums[right]))
@@ -828,16 +823,14 @@ comments: true
}
/* 哨兵划分（三数取中值） */
int partition(int[] nums, int left, int right)
{
int partition(int[] nums, int left, int right) {
// 选取三个候选元素的中位数
int med = medianThree(nums, left, (left + right) / 2, right);
// 将中位数交换至数组最左端
swap(nums, left, med);
// 以 nums[left] 作为基准数
int i = left, j = right;
while (i < j)
{
while (i < j) {
while (i < j && nums[j] >= nums[left])
j--; // 从右向左找首个小于基准数的元素
while (i < j && nums[i] <= nums[left])
@@ -1063,21 +1056,16 @@ comments: true
```csharp title="quick_sort.cs"
/* 快速排序（尾递归优化） */
void quickSort(int[] nums, int left, int right)
{
void quickSort(int[] nums, int left, int right) {
// 子数组长度为 1 时终止
while (left < right)
{
while (left < right) {
// 哨兵划分操作
int pivot = partition(nums, left, right);
// 对两个子数组中较短的那个执行快排
if (pivot - left < right - pivot)
{
if (pivot - left < right - pivot) {
quickSort(nums, left, pivot - 1); // 递归排序左子数组
left = pivot + 1; // 剩余待排序区间为 [pivot + 1, right]
}
else
{
} else {
quickSort(nums, pivot + 1, right); // 递归排序右子数组
right = pivot - 1; // 剩余待排序区间为 [left, pivot - 1]
}