快速排序

#include <iostream>
#include <vector>

using namespace std;

template <typename Comparable>
void insertionSort( vector<Comparable> &a,int left,int right )
{
    int j;

    for ( int p = left + 1 ; p < right + 1 ; p++ ){
        Comparable tmp = a[p];                          //保存当前元素值
        for ( j = p ; j > left && tmp < a[j - 1] ; j-- )   //通过循环将位置p之前比p大的元素都向右移一格
            a[j] = a[j - 1];
        a[j] = tmp;                                     //最后在适当的位置插入元素值.
    }
}


template <typename Comparable>
const Comparable &median3( vector<Comparable> &a,int left,int right )
{
    int center = ( left + right ) / 2;
    if ( a[center] < a[left] )
        swap( a[left],a[center] );
    if ( a[right] < a[left] )
        swap( a[left],a[right] );
    if ( a[right] < a[center] )
        swap( a[center],a[right] );

    swap( a[center],a[right - 1] );
    return a[right - 1];
}

template <typename Comparable>
void quicksort( vector<Comparable> &a,int left,int right )
{
    if ( left + 10 <= right ){
        Comparable pivot = median3( a,left,right );

        int i = left,j = right - 1;
        for ( ; ; ){
            while( a[++i] < pivot ) {}
            while ( pivot < a[--j] ) {}
            if ( i < j )
                swap( a[i],a[j] );
            else
                break;
        }

        swap( a[i],a[right - 1] );

        quicksort( a,left,i - 1 );
        quicksort( a,i + i,right );
    }
    else
        insertionSort( a,left,right );
}

template <typename Comparable>
void quicksort( vector<Comparable> &a )
{
    quicksort( a,0,a.size() - 1 );
}

int main()
{
    cout << "请输入一些数据：" << endl;

    vector<int> vec;
    int temp;

    while ( cin >> temp )
        vec.push_back( temp );

    quicksort( vec );

    cout << "按升序排列过的数据如下：" << endl;

    vector<int>::iterator iter = vec.begin();
    while( iter != vec.end() )
        cout << *iter++ << endl;

    return 0;
}