快速排序——C++左闭右开区间实现

代码

---

#include<iostream>
#include<vector>
using namespace std;
class Solution
{
public:
    //快速排序接口
    void quickSort(vector<int> &vec, vector<int>::iterator begin, vector<int>::iterator end)
    {
        if (end != vec.begin() && begin < end - 1)
        {
            vector<int>::difference_type pivot = partition(vec, begin, end - 1);
            quickSort(vec, begin, vec.begin() + pivot);
            quickSort(vec, vec.begin() + pivot + 1, end);
        }
    }
private:
    //实现移动
    vector<int>::difference_type partition(vector<int> &vec, vector<int>::iterator begin, vector<int>::iterator end)
    {
        findMidOfThree(vec,begin,end);
        while (begin < end)
        {
            while (begin < end && *begin < *end) end--;
            swap(*begin, *(end));
            while (begin < end && *begin < *(end)) begin++;
            swap(*begin, *(end));

        }
        return begin-vec.begin();
    }
    //实现查找中位数并且交换位置，防止达到最坏复杂度
    void findMidOfThree(vector<int> &vec, vector<int>::iterator begin, vector<int>::iterator end)
    {
        vector<int>::iterator midIter = (begin + (end-begin)/2);
        if ((*begin > *end&&*begin < *midIter) ||
            (*begin<*end&&*begin>*midIter))
            return;
        if ((*midIter > *begin&&*midIter < *end) ||
            (*midIter > *end&&*midIter < *begin))
            swap(*midIter, *begin);
        if ((*end > *begin&&*end < *midIter) ||
            (*end > *midIter&&*end < *begin))
            swap(*end, *begin);
    }
};

#include"快速排序.h"
void main()
{
    Solution s;
    vector<int> test = { 1,3,5,7,9,2,4,6,8,10 };
    s.quickSort(test, test.begin(), test.end());

    for (auto i : test)
    {
        cout << i << " ";
    }
    cout << endl;
}

总结

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最难的一点就是要控制左闭右开的区间，一些边界条件非常难控制。