选择排序

 

 

选择排序算法：

void selectionSort(int arr[], int n){

    for(int i = 0 ; i < n ; i ++){

        int minIndex = i;
        for( int j = i + 1 ; j < n ; j ++ )
            if( arr[j] < arr[minIndex] )
                minIndex = j;

        swap( arr[i] , arr[minIndex] );
    }
}

 

自定义结构体：

#ifndef INC_02_SELECTION_SORT_USING_TEMPLATE_STUDENT_H
#define INC_02_SELECTION_SORT_USING_TEMPLATE_STUDENT_H
#include <iostream>
#include <string>
using namespace std;
struct Student{
    string name;
    int score;
    bool operator<(const Student& otherStudent){
        return score != otherStudent.score ?
               score > otherStudent.score : name < otherStudent.name;
    }
    friend ostream& operator<<(ostream &os, const Student &student){

        os<<"Student: "<<student.name<<" "<<student.score<<endl;
        return os;
    }
};

#endif //INC_02_SELECTION_SORT_USING_TEMPLATE_STUDENT_H

 

 

使用模板函数：

#include <iostream>
#include "Student.h"

using namespace std;

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

    for(int i = 0 ; i < n ; i ++){

        int minIndex = i;
        for( int j = i + 1 ; j < n ; j ++ )
            if( arr[j] < arr[minIndex] )
                minIndex = j;

        swap( arr[i] , arr[minIndex] );
    }
}

int main() {

    // 测试模板函数，传入整型数组
    int a[10] = {10,9,8,7,6,5,4,3,2,1};
    selectionSort( a , 10 );
    for( int i = 0 ; i < 10 ; i ++ )
        cout<<a[i]<<" ";
    cout<<endl;

    // 测试模板函数，传入浮点数数组
    float b[4] = {4.4,3.3,2.2,1.1};
    selectionSort(b,4);
    for( int i = 0 ; i < 4 ; i ++ )
        cout<<b[i]<<" ";
    cout<<endl;

    // 测试模板函数，传入字符串数组
    string c[4] = {"D","C","B","A"};
    selectionSort(c,4);
    for( int i = 0 ; i < 4 ; i ++ )
        cout<<c[i]<<" ";
    cout<<endl;

    // 测试模板函数，传入自定义结构体Student数组
    Student d[4] = { {"D",90} , {"C",100} , {"B",95} , {"A",95} };
    selectionSort(d,4);
    for( int i = 0 ; i < 4 ; i ++ )
        cout<<d[i];
    cout<<endl;

    return 0;
}

 

SortTestHelper添加对算法效率的衡量：

 template<typename T>
    bool isSorted(T arr[], int n) {//是否被正确的排序

        for (int i = 0; i < n - 1; i++)
            if (arr[i] > arr[i + 1])
                return false;

        return true;
    }

    template<typename T>
    void testSort(const string &sortName, void (*sort)(T[], int), T arr[], int n) {//通过指定函数的名称、测试算法函数的地址、测试的数组、长度对数组进行时间的判断

        clock_t startTime = clock();
        sort(arr, n);
        clock_t endTime = clock();

        assert(isSorted(arr, n));
        cout << sortName << " : " << double(endTime - startTime) / CLOCKS_PER_SEC << " s" << endl;

        return;
    }

 

测试：

int main() {

    int n = 10000;
    int *arr = SortTestHelper::generateRandomArray(n,0,n);
    SortTestHelper::testSort("Selection Sort", selectionSort, arr, n);
    delete[] arr;

    return 0;
}