public int[] Sort(int[] arr)
{
int length = arr.Length;
for (int i = 0; i < length - 1; i++)
{
for (int j = 0; j < length - i - 1; j++)
{
if (arr[j + 1] < arr[j])
{
SortHelp.Swap(arr, j, j + 1);
}
}
}
return(arr);
}
public int[] Sort(int[] arr)
{
int length = arr.Length;
for (int i = 0; i < length; i++)
{
for (int j = i + 1; j < length - 1; j++)
{
if (arr[j] < arr[i])
{
SortHelp.Swap(arr, i, j);
}
}
}
return(arr);
}
/*
* Heap Sort：Heap sort is a comparison based sorting technique based on Binary Heap data structure.
* 1. Build a max heap from the input data.
* 2. 第一个元素和最后一个元素交换位置，然后 heaptiy 第一个元素
* 3. 重复交换，重复堆化
* Time Complexity: O(nlogn)
*/
public int[] Sort(int[] arr)
{
int arrsize = arr.Length;
int index = arrsize / 2 - 1;
for (int i = index; i >= 0; i--)
{
Heapify(arr, arrsize, i);
}
for (int i = arrsize - 1; i >= 0; i--)
{
SortHelp.Swap(arr, i, 0);
Heapify(arr, i, 0);
}
return(arr);
}
public int[] Sort(int[] arr)
{
int length = arr.Length;
for (int gap = length / 2; gap > 0; gap /= 2)
{
for (int i = gap; i < length; i++)
{
for (int j = i; j - gap >= 0; j -= gap)
{
if (arr[j] < arr[j - gap])
{
SortHelp.Swap(arr, j, j - gap);
}
}
}
}
return(arr);
}
private int[] QuickSort(int[] arr, int left, int right)
{
if (left < right)
{
int pivot = Pivot(arr, left, right);
int i = left;
int j = right - 1;
for (; ;)
{
while (i < arr.Length && arr[++i] < pivot)
{
}
while (j > 0 && arr[--j] > pivot)
{
}
if (i < j)
{
SortHelp.Swap(arr, i, j);
}
else
{
break;
}
}
// 把锚点交换成正确的位置
if (i < right - 1)
{
SortHelp.Swap(arr, i, right - 1);
}
QuickSort(arr, left, i - 1);
QuickSort(arr, i + 1, right);
}
return(arr);
}
public void Heapify(int[] arr, int arrsize, int index)
{
int left = 2 * index + 1;
int right = 2 * index + 2;
int larget = index;
if (left > 0 && left < arrsize && arr[left] > arr[larget])
{
larget = left;
}
if (right > 0 && right < arrsize && arr[right] > arr[larget])
{
larget = right;
}
if (larget != index)
{
SortHelp.Swap(arr, index, larget);
Heapify(arr, arrsize, larget);
}
}
private int Pivot(int[] arr, int left, int right)
{
int center = (left + right) / 2;
if (arr[left] > arr[center])
{
SortHelp.Swap(arr, left, center);
}
if (arr[right] < arr[left])
{
SortHelp.Swap(arr, left, right);
}
if (arr[right] < arr[center])
{
SortHelp.Swap(arr, right, center);
}
// 如果只有三个数，那么前面的步骤已经排序
if (left + 2 < right)
{
SortHelp.Swap(arr, center, right - 1);
}
return(arr[right - 1]);
}