<分区>
我正在使用的代码来自 Ivor Horton 的“Beginning Visual C++ 2010”。 特别是 Ex10_02.cpp 使用 Person.h。
sort 函数对我的类对象不起作用。当输入姓名并最终按下 Enter 键时，姓名列表按照输入中给定的顺序输出，在调用 sort() 函数后，姓名再次输出到屏幕。它们应该根据第二个名字进行排序。但它们的输出顺序与我最初输入它们的顺序相同。
我没有得到任何编译错误。我已经为我的类测试了 operator<() ，它在比较 Person 类的两个对象时有效。但是，用于 Person 对象 vector 的 sort() 函数再次无法正常工作。我对为什么会这样没有更多的想法。欢迎任何见解。
代码如下:
// Ex10_02
// storing objects in a vector
#include <iostream>
#include <vector>
#include <algorithm>
#include "Person.h"
using namespace std;
int main()
{
vector<Person> people; // Vector of Person objects
const size_t maxlength(50);
char firstname[maxlength];
char secondname[maxlength];
vector<int> numbers;
// input all the people
while(true)
{
cout << "Enter a first name or press Enter to end:";
cin.getline(firstname, maxlength, '\n');
if(strlen(firstname) == 0)
break;
cout << "Enter the second name: ";
cin.getline(secondname, maxlength, '\n');
people.push_back(Person(firstname, secondname));
}
// Output the contents of the vector
cout << endl;
auto iter(people.begin());
while(iter != people.end())
iter++->showPerson();
sort(people.begin(), people.end());
cout << endl;
for(auto i = 0; i < people.size(); i++)
{
people[i].showPerson();
}
cout << endl;
for(auto i = 0; i < people.size(); i++)
{
people[i].showPerson();
}
cout << endl;
cout << "Is people[0] < people[1] ?" << endl;
if(people[0] < people[1])
{
cout << "YES" << endl;
people[0].showPerson ();
people[1].showPerson();
}
else
{
cout << "NO" << endl;
people[1].showPerson();
people[0].showPerson();
}
cout << endl;
int myints[] = {32,71,12,45,26,80,53,33};
vector<int> myvector (myints, myints+8); // 32 71 12 45 26 80 53 33
for(int i = 0; i < 8; i++)
cout << myvector[i] << endl;
cout << endl;
// using default comparison (operator <):
sort(myvector.begin(), myvector.end()); //(12 32 45 71)26 80 53 33
for(int i = 0; i < 8; i++)
cout << myvector.at(i) << endl;
return 0;
}
//-----------------------------------------------------------------------
Person.h:
// A class defining people by their names
//#pragma once
#ifndef PERSON_H_INCLUDED
#define PERSON_H_INCLUDED
#include <cstring>
#include <iostream>
using namespace std;
class Person
{
public:
// Constructor, includes no-arg constructor
Person(const char* first = "John", const char* second = "Doe")
{
initName(first, second);
}
// Copy constructor
Person(const Person& p)
{
initName(p.firstname, p.secondname);
}
// Destructor
~Person()
{
delete[] firstname;
delete[] secondname;
}
// Assignment operator
Person& operator =(const Person& p)
{
// deal with p = p assignment situation
if(&p == this)
{
return *this;
delete[] firstname;
delete[] secondname;
initName(p.firstname, p.secondname);
return *this;
}
}
// Less-than operator
bool operator <(const Person& p)
{
int result(strcmp(secondname, p.secondname));
if(result < 0 || result == 0 && strcmp(firstname, p.firstname) < 0)
return true;
return false;
}
// output a person
void showPerson() const
{
cout << firstname << " " << secondname << endl;
}
private:
char* firstname;
char* secondname;
// private helper function to avoid code duplication
void initName(const char* first, const char* second)
{
size_t length(strlen(first)+1);
firstname = new char[length];
strcpy_s(firstname, length, first);
length = strlen(second) + 1;
secondname = new char[length];
strcpy_s(secondname, length, second);
}
};
#endif // PERSON_H_INCLUDED