排序-006-Quick-Sort-03-Deal-With-Identical-Keys

最新推荐文章于 2024-06-14 16:13:27 发布

转载最新推荐文章于 2024-06-14 16:13:27 发布 · 129 阅读

数据结构与算法专栏收录该内容

57 篇文章

订阅专栏

本文通过三种不同类型的数组：随机数组、近乎有序数组和包含大量重复元素的数组，对比了快速排序与归并排序的性能。实验结果显示，在一般情况下，快速排序表现优于归并排序，但在近乎有序的数组上，归并排序更胜一筹。

main.cpp

#include <iostream>
#include <algorithm>
#include <ctime>
#include "SortTestHelper.h"
#include "MergeSort.h"
#include "InsertionSort.h"

using namespace std;


template <typename T>
int _partition(T arr[], int l, int r){

    swap( arr[l] , arr[rand()%(r-l+1)+l] );

    T v = arr[l];
    int j = l;
    for( int i = l + 1 ; i <= r ; i ++ )
        if( arr[i] < v ){
            j ++;
            swap( arr[j] , arr[i] );
        }

    swap( arr[l] , arr[j]);

    return j;
}

template <typename T>
int _partition2(T arr[], int l, int r){

    swap( arr[l] , arr[rand()%(r-l+1)+l] );
    T v = arr[l];

    // arr[l+1...i) <= v; arr(j...r] >= v
    int i = l+1, j = r;
    while( true ){
        while( i <= r && arr[i] < v )
            i ++;

        while( j >= l+1 && arr[j] > v )
            j --;

        if( i > j )
            break;

        swap( arr[i] , arr[j] );
        i ++;
        j --;
    }

    swap( arr[l] , arr[j]);

    return j;
}

template <typename T>
void _quickSort(T arr[], int l, int r){

//    if( l >= r )
//        return;
    if( r - l <= 15 ){
        insertionSort(arr,l,r);
        return;
    }

    int p = _partition2(arr, l, r);
    _quickSort(arr, l, p-1 );
    _quickSort(arr, p+1, r);
}

template <typename T>
void quickSort(T arr[], int n){

    srand(time(NULL));
    _quickSort(arr, 0, n-1);
}


int main() {

    int n = 1000000;

    // 测试1 一般性测试
    cout<<"Test for Random Array, size = "<<n<<", random range [0, "<<n<<"]"<<endl;
    int* arr1 = SortTestHelper::generateRandomArray(n,0,n);
    int* arr2 = SortTestHelper::copyIntArray(arr1,n);

    SortTestHelper::testSort("Merge Sort", mergeSort, arr1, n);
    SortTestHelper::testSort("Quick Sort", quickSort, arr2, n);

    delete[] arr1;
    delete[] arr2;

    cout<<endl;


    // 测试2 测试近乎有序的数组
    int swapTimes = 100;
    cout<<"Test for Random Nearly Ordered Array, size = "<<n<<", swap time = "<<swapTimes<<endl;
    arr1 = SortTestHelper::generateNearlyOrderedArray(n,swapTimes);
    arr2 = SortTestHelper::copyIntArray(arr1, n);

    SortTestHelper::testSort("Merge Sort", mergeSort, arr1, n);
    SortTestHelper::testSort("Quick Sort", quickSort, arr2, n);

    delete[] arr1;
    delete[] arr2;

    cout<<endl;


    // 测试3 测试存在包含大量相同元素的数组
    cout<<"Test for Random Array, size = "<<n<<", random range [0,10]"<<endl;
    arr1 = SortTestHelper::generateRandomArray(n,0,10);
    arr2 = SortTestHelper::copyIntArray(arr1, n);

    SortTestHelper::testSort("Merge Sort", mergeSort, arr1, n);
    SortTestHelper::testSort("Quick Sort", quickSort, arr2, n);

    delete[] arr1;
    delete[] arr2;


    return 0;
}