【算法】测试数组逆序对个数算法（C++源码）

【算法】测试数组逆序对个数算法（C++源码）

一、任务描述

给定一个整数数组A=(a0, a1,…,an-1)，若i<j且ai > aj,则<ai,aj>就为一个逆序对。例如数组(3,1,4,5,2)的 逆序对有<3,1>, < 3,2>,<4,2>,<5,2>。请编写并测试 求A中逆序对个数的算法，并分析其时间复杂度。

二、步骤描述

随机生成数暴力求解，时间复杂度O(n²)

三、运行结果截图

四、源代码（C++）

#include<iostream>
#include<ctime>
#include<Windows.h>

using namespace std;

int main()
{
    DWORD start_time=GetTickCount();
    srand(time(NULL));
    int n;
    cout<<"Please enter the number of array size :";
    cin>>n;
    int a[n],i,j,count=0;
    cout<<n<<" random arrays are being generated,please wait !"<<endl;
    for(i=0;i<n;i++)
    {
        a[i]=rand()%10;
    }
    cout<<n<<" random arrays generation completed !"<<endl;
    cout<<n<<" random arrays print :";
    for(i=0;i<n;i++)
    {
        cout<<a[i]<<" ";
    }
    cout<<endl;
    for(i=0;i<n-1;i++)
    {
        for(j=i+1;j<n;j++)
        {
            if(a[i]>a[j])
            {
                cout<<"<"<<a[i]<<","<<a[j]<<">"<<" ";
                count++;
            }
        }
    }
    cout<<endl;
    cout<<"The number of reverse alignment is :"<<count<<endl;
    DWORD end_time = GetTickCount();
    cout<<"The run time is :"<<(end_time-start_time)<<"ms!"<<endl;
    return 0;
}