Randomized_QuickSort C++

算法导论(第三版)中文 P102

 

 //RANDOMIZED_QUICKSORT.h文件

 1 #pragma once
#include"QUICKSORT.h"
#include<iostream>
#include<random>
int Randomized_partition(std::vector<int>& A, const int& p, const int& r)
{
    std::default_random_engine e; //引擎：生成随机无符号数
    std::uniform_int_distribution<unsigned> u(p, r);// 范围内的随机数
    int i = u(e);
    std::swap(A[r], A[i]); //是随机数是主元
    return Partition(A, p, r);
}

void Randomized_QuickSort(std::vector<int> &A, const int& p, const int& r)
{
    if (p < r)
    {
        int q = Randomized_partition(A, p, r);
        Randomized_QuickSort(A, p, q-1);
        Randomized_QuickSort(A, q + 1, r);
    }
}

main.cpp

#include"QUICKSORT.h"
#include"RANDOMIZED_QUICKSORT.h"
#include<iterator> //ostream_iterator
void QuickSort()
{
    vector<int> v = { 0,2,8,7,1,3,5,6 };//0 占位置 是 i = p-1;
    cout << "A is" << endl;
    std::ostream_iterator<int> out_iter(cout, " ");
    copy(v.begin() + 1, v.end(), out_iter);
    cout << endl;
    Randomized_QuickSort(v, 1, v.size()-1);
    cout << " sorted A " << endl;
    copy(v.begin() + 1, v.end(), out_iter);
}
int main()
{
    QuickSort();
}