快速排序(C++实现)

1.分治思想

选取基数，通过交换，将小的分左边一组，大的分右边一组，基数放在中间

2.递归思想

对小的或大的一组重复进行分类，直到组的大小为1或0

C++ main.cc

#include <iostream>
using namespace std;

const int N=12;
int arr[N] = {3,7,9,2,6,1,5,4,8,19,15};

void swap(int * arr, int i, int j)
{
    int tmp = arr[i];
    arr[i] = arr[j];
    arr[j] = tmp;

}
//输入左下标，右下标
//返回中间元素位置
int part(int arr[], int left,int right)
{
    int middle = left;
    int base = arr[left];
    for(int i = left+1;i <= right;i++)
    {
        if(arr[i] < base)
        {
            swap(arr,i,middle+1);
            middle++;
        }

    }
    swap(arr,left,middle);
    for(int i = 0; i<N;i++) 
    {
        cout << arr[i] << ' ';
    }
    cout << endl;
    return middle;

}
void quick_sort(int arr[],int left,int right)
{
    if(left < right)
    { 
        int index = part(arr,left,right);
        quick_sort(arr, left, index-1);
        quick_sort(arr, index+1, right);
    }
    else
    {
    	return;
    }
}
int main(/**argc **argv[]*/)
{
    for(int i = 0; i<N;i++) 
    {
        cout << arr[i] << ' ';
    }
    cout << endl;
    
    //int num = part(arr,0,N-1);
    quick_sort(arr,0,N-1);

    for(int i = 0; i<N;i++) 
    {
        cout << arr[i] << ' ';
    }
    //cout << num << endl;
    cout << endl;
    return 0;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.5)
project(quick_sort)

#aux_source_directory(SOURCE ./)
add_executable(quick_sort main.cc)
#target_link_library(quick_sort)