c++ - 如何在不更改原始数组的情况下对指向结构的指针数组进行排序？

Question

我对 C++ 和指针相当陌生，非常感谢任何帮助。我试图在不更改原始结构数组的情况下打印一个排序的指针数组。我无法正确排序指针。我正在使用在原始数组上工作的 std::sort，但我无法在指针上使用它。更糟糕的是，我失败的尝试全部改变了原来的。感谢您的时间。

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <string.h>

using namespace std;

struct Student
{
    int age;
    char name[30];

};

void displayStudent(Student s)
{

    cout << endl<< s.age<< "    "<< s.name;

}


int main()
{
    Student s1;
    s1.age = 10;
    strcpy(s1.name, "Guy");

    Student s2;
    s2.age = 33;
    strcpy(s2.name, "Buddy");

    Student s3;
    s3.age = 16;
    strcpy(s3.name, "Friend");

    Student s4;
    s4.age = 55;
    strcpy(s4.name, "Pal");

    Student myClass[4];
    myClass[0] = s1;
    myClass[1] = s2;
    myClass[2] = s3;
    myClass[3] = s4;

    Student *myClassPt;
    myClassPt = &myClass[0];
    Student *SBN[4];
    Student *SBG[4];
    Student *SBA[4];
    for (int i = 0; i < 4; i++)
    {
        SBN[i] = &(myClassPt[i]);
        SBA[i] = &(myClassPt[i]);

    }
    cout << "Original" << endl;
    for (int i = 0; i < 4; i++)
    {
        displayStudent(myClass[i]);
    }

    std::sort(*SBN, *SBN + 4, [](Student  &a, Student  &b){ return a.name < b.name; });
    std::sort(*SBA, *SBA + 3, [](Student const &a, Student const &b){ return a.age < b.age; });

    cout <<endl<<endl<< "Sorted by name" << endl;
    for (int i = 0; i < 4; i++)
    {
        displayStudent(*SBN[i]);
    }
    cout << endl << endl << "Sorted by age" << endl;
    for (int i = 0; i < 4; i++)
    {
        displayStudent(*SBA[i]);
    }

    cout << endl <<endl<< "Original" << endl;
    for (int i = 0; i < 4; i++)
    {
        displayStudent(myClass[i]);
    }

    return 0;
}

Answer 1

您似乎想根据指针所指向的对象对指针进行排序。所以你需要根据指针指向的对象对指针进行排序，而不是试图直接对它们指向的对象进行排序:

std::sort(SBN, SBN + 4, [](const Student* a, const Student* b)
                        { return a->name < b->name; });

这是一个工作示例:

#include <iostream>
#include <algorithm>

struct student { int age; };

int main()
{
  student ss[] = { {23}, {12}, {42}, {9}};
  std::cout << "students\n";
  for (const auto& s : ss) std::cout << s.age << " ";
  std::cout << std::endl;

  student* ps[] = { &ss[0], &ss[1], &ss[2], &ss[3]};
  std::cout << "pointers to student\n";
  for (auto p : ps) std::cout << p->age << " ";
  std::cout << std::endl;

  std::sort(ps, ps + 4, [](const student* a, const student* b)
                        { return a->age < b->age;});
  std::cout << "pointers to student after sorting\n";
  for (auto p : ps) std::cout << p->age << " ";
  std::cout << std::endl;
}

输出:

students
23 12 42 9 
pointers to student
23 12 42 9 
pointers to student after sorting
9 12 23 42