快速排序算法

方法一： 

#include <iostream>
#include <vector>
using namespace std;

void Quick_Sort(vector<int> &data, int left, int right)
{
    if (left < right)
    {
        int i = left, j = left;
        int pivot = data[right];

        for (j = left; j < right; j++)
        {
            if (data[j] < pivot)
            {
                swap(data[i], data[j]);
                ++i;
            }
        }
        data[j] = data[i];
        data[i] = pivot;
        Quick_Sort(data, left, i - 1);
        Quick_Sort(data, i + 1, right);
    }
}

int main()
{
    vector<int> vec;
    int n;
    cin >> n;
    for (int i = 0; i < n; i++)
    {
        int a;
        cin >> a;
        vec.push_back(a);
    }
    cout << "排序前：";
    for (auto c : vec)
        cout << c << " ";
    cout << endl;
    Quick_Sort(vec, 0, vec.size() - 1);
    cout << "排序后：";
    for (auto c: vec)
        cout << c << " ";
    system("pause");
    return 0;
}

 

 

算法二：

#include <iostream>
#include <vector>
using namespace std;

void Quick_Sort(vector<int>& data, int left, int right)
{
    if (left < right)
    {
        int i = left, j = right;
        int pivot = data[j];
        while (i < j)
        {
            while (i < j && data[i] <= pivot) // 从左往右找到第一个比 pivot 大的数
                i++;

            if (i < j)
                data[j--] = data[i];

            while (i < j && data[j] >= pivot) // 从右往左找到第一个比 pivot 小的数
                j--;

            if (i < j)
                data[i++] = data[j];
        }
        data[i] = pivot;
        Quick_Sort(data, left, i - 1);
        Quick_Sort(data, i + 1, right);
    }
}

int main()
{
    int n;
    cin >> n;
    vector<int> data;
    for (int i = 0; i < n; ++i)
    {
        int a;
        cin >> a;
        data.push_back(a);
    }
    Quick_Sort(data, 0, data.size() - 1);
    for (auto c : data)
        cout << c << " ";
    return 0;
}