搜索類型數組的數組

Question

我正在研究這個控制學生信息的C++程序。我已經能夠添加和顯示學生的信息。我需要通過他的ID在特定學生的數組中搜索數組，但是爲了搜索ID，似乎將類型類的數組賦值給int變量時出現問題？

#include <iostream> 
#include <string> 
#include <array> 
#include <iomanip> 

using namespace std; 

class student{ 
private: 
    int id, age; 
    std::string fname, lname; 
    string cob; 
    char s; 
public: 

    student() 
    { 
     id=age=0; 
     fname=lname=cob=""; 
    } 

    void setid(int); 
    void setage(int); 
    void setfname(string); 
    void setlname(string); 
    void setsex(char); 
    void setcob(string); 

    int getid(); 
    int getage(); 
    string getfname(); 
    string getlname(); 
    string getcob(); 
    char getsex(); 
}; 

void student::setfname(string n) 
{ fname=n;} 
void student::setlname(string n) 
{ lname=n;} 
void student::setcob(string n) 
{ cob=n;} 
void student::setid(int n) 
{ id=n;} 
void student::setage(int n) 
{ age=n;} 
void student::setsex(char n) 
{ s=n;} 


string student::getfname() 
{ return fname;} 
string student::getlname() 
{ return lname;} 
string student::getcob() 
{ return cob;} 
int student::getid() 
{ return id;} 
int student::getage() 
{ return age;} 
char student::getsex() 
{ return s;} 


std::array<student, 100> studentlist; 

void addstd() 
{ 
    int id, age; 
    string fname, lname; 
    string cob; 
    char s; 
    for(int i=0;i<3;i++) 
      { 
       cout<<"Enter ID Number"<<endl; 
       cin>>id; 
       studentlist[i].setid(id); 
       cout<<"Enter First Name"<<endl; 
       cin>>fname; 
       studentlist[i].setfname(fname); 
       cout<<"Enter last Name"<<endl; 
       cin>>lname; 
       studentlist[i].setlname(lname); 
       cout<<"Enter age"<<endl; 
       cin>>age; 
       studentlist[i].setage(age); 
       cout<<"Enter student's Sex(F or M) "<<endl; 
       cin>>s; 
       studentlist[i].setsex(s); 
       cout<<"Enter Country of birth"<<endl; 
       cin>>cob; 
       studentlist[i].setcob(cob); 
      } 
} 
void displayinfo() 
{ 
    for(int i=0;i<3;i++) 
    { 
     cout<<"Student ID: "<<studentlist[i].getid()<<endl; 
     cout<<"First Name: "<<studentlist[i].getfname()<<endl; 
     cout<<"Last Name: "<<studentlist[i].getlname()<<endl; 
     cout<<"Student Age: "<<studentlist[i].getage()<<endl; 
     cout<<"Student Gender: "<<studentlist[i].getsex()<<endl; 
     cout<<"Student Birth City: "<<studentlist[i].getcob()<<endl; 
     cout<< "\n"; 
    } 
} 

void searchstd() 
{ 
    int num; 
    cout<<"Enter ID of Student "<<endl; 
    cin>>num; 
    int temp; 
    for(int i=0;i<3;i++) 
    { 
     studentlist[i]=temp; // here is the problem!! 
     if(temp==num) 
     { 

     } 
    } 
} 


/*std::array<student, 100> studentlist;*/ 

void main() 
{ 
    /* 
    student s; 
    student std[100]; 
    */ 
    student s; 

    int choice; 

    do{ 

    cout << "-----------Menu------------" << endl; 
     cout << " 1. Add a student " << endl; 
     cout << " 2. Search for student by ID " << endl; 
     cout << " 3. Display all students information " << endl; 
     cout << " 4. Remove a students " << endl; 
     cout << " 5. Display students aged between 34 - 50 " << endl; 
     cout << " 6. Modify a student's information   " << endl; 
     cout << " 7. Exit   " << endl; 
     cout << " Enter your choice 1, 2, 3, 4 ,5,6,7 " << endl; 
    cin>>choice; 

    switch(choice) { 
     case 1: 
      addstd(); 
      break; 
     case 2: 
      searchstd(); 
      break; 
     case 3: 
      displayinfo(); 
      break; 
     case 4: 
      break; 
     case 5: 
      break; 
     case 6: 
      break; 
     case 7: 
      exit(0); 
      break; 
     default: 
      cout << "Please enter 1, 2, 3, 4, 5, 6 or 7 : " << endl << endl; 
    } 

    }while(choice!=8); 

} 

Answer 1

studentlist[i]=temp; // here is the problem!! 

studentlist[]是類student的對象的數組，並temp是int類型的變量。這是無效的。您正嘗試將uninitialized int（可能有任何值）分配給students的數組。

我相信，通過看你的實現，你正在尋找這樣的事情（儘管搜索可以改進）：

int num; 
cout<<"Enter ID of Student "<<endl; 
cin>>num; 

for(int i=0;i<3;i++) 
{ 
    if(studentlist[i].getid() == num) 
    { 
     // found student with id == num 
    } 
}