快速排序的实现

最新推荐文章于 2023-02-14 00:09:48 发布

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本文通过详细的代码示例介绍了快速排序算法的实现方式，并讨论了在排序过程中处理重复元素的重要性，以避免算法陷入死循环或出现不正确的中间状态。

直接上代码，里面有一个注意点就是当从右向左的时候（假设是按升序来排序），对于跟基准值相等的元素一定要进行处理，而不是跳过。或者从左向右的时候，对于跟基准值相等的一定要跳过，否则容易进入死循环，或者对有重复数字的数据中间过程有“假”快速排序的情况（比如2 2 9 1 2 3，第一次循环很可能就变成了2 2 1 9 2 3，虽然最终结果是对的，但是这一步并没有把数据按照基准值进行划分）。

#include "stdafx.h"

#include <iostream>

#include <vector>

using namespace std;

#pragma region Sort

namespace Sort

{

int iArray[] = { 3, 8, 1, 6, 2, 5, 4, 9, 7 };

int iArray1[] = { 2,2,18,9,1,3,2,0,19,20,15,6,12 };

int iArray2[] = { 2,1,1,2 };

vector<int>iVector = { 3, 8, 1, 6, 2, 5, 4, 9, 7 };

void QuickSort(int data[], int left, int right)

{

if (left >= right)

return;

int start = left, end = right;

int temp = data[left];

while (end > start)

{

while (end > start && data[end] > temp)

end--;

while (end > start && data[start] <= temp)

start++;

if (end > start)

{

int leftTemp = data[start];

data[start] = data[end];

data[end] = leftTemp;

}

data[left] = data[end];

data[end] = temp;

QuickSort(data, left, end - 1);

QuickSort(data, end + 1, right);

}

void QuickSort2(int data[], int left, int right)

{

if (left >= right)

return;

int start = left, end = right;

int base = data[start];

while (end > start)

{

while (end > start && data[end] > base)

end--;

data[start] = data[end];

while (end > start && data[start] <= base)

start++;

data[end] = data[start];

}

data[start] = base;

QuickSort2(data, left, end - 1);

QuickSort2(data, end + 1, right);

}

void QuickSortWithComment(int data[], int left, int right)

{

if (left >= right)

{

cout << "******Startindex " << left << " >=end index " << right << endl;

return;

}

cout << "Sorting";

for (int i = left; i <= right; i++)

{

cout << "_" << data[i];

}

cout << endl;

int start = left, end = right;

int temp = data[left];

while (end > start)

{

while (end > start && data[end] > temp)

end--;

while (end > start && data[start] <= temp)

start++;

if (end > start)

{

int leftTemp = data[start];

data[start] = data[end];

data[end] = leftTemp;

}

data[left] = data[end];

data[end] = temp;

cout << "TempResult with KEY: " << temp << ":";

for (int i = left; i <= right; i++)

{

if (i == end)

{

cout << "_(" << data[i] << ")";

}

else

{

cout << "_" << data[i];

}

cout << endl;

QuickSort(data, left, end - 1);

QuickSort(data, end + 1, right);

cout << "Resultwith KEY: " << temp << ":";

for (int i = left; i <= right; i++)

{

cout << "_" << data[i];

}

cout << endl;

}

int Patition(int data[], int left, int right)

{

if (left < right)

{

int base = data[left];

while (left < right)

{

while (left < right&& data[right] > base)

right--;

data[left] = data[right];

while (left < right&& data[left] <= base)

left++;

data[right] = data[left];

}

data[left] = base;

}

return left;

}

void QuickSortWithoutRecursive(int data[], int left, int right)

{

if (left < right)

{

stack<int> st;

st.push(right);

st.push(left);

while (!st.empty())

{

left = st.top();

st.pop();

right = st.top();

st.pop();

int patition = Patition(data, left, right);

if (patition > left)

{

st.push(patition- 1);

st.push(left);

}

if (patition < right)

{

st.push(right);

st.push(patition+ 1);

}

void TestQuickSort()

{

//QuickSortWithoutRecursive(iArray,0, 8);

//QuickSortWithoutRecursive(iArray1,0, 12);

//QuickSortWithoutRecursive(iArray2,0, 3);

//QuickSort(iArray,0, 8);

//QuickSort(iArray1,0, 12);

QuickSort2(iArray1, 0, 12);

//QuickSort(iArray2,0,3);

QuickSort2(iArray2, 0, 3);

}

#pragma endregion

#define TEST(uSpace,method)\

using namespace uSpace;\

method;\

}

int main()

{

TEST(Sort, TestQuickSort());

return 0;

}