searching through an array of class objects c++

Question

I need help trying to search an array of class objects. I have a class called users and have an array where 3 players are stored. I would like to be able to show the information of a particular player when his both names are typed in and delete his records when is name is typed in.

I understand that I could use a vector list to make this easier, but I have limitations set. I also think a linear search could be implemented but i don't know if that is efficient enough.

#include <iostream>
#include <string>
#include <math.h>

using namespace std;

void storeinfo() ;
void showinfo() ;
void menu() ;


class user 
{
    string firstname, lastname, currentteam, position, status ;
    int age ;
public:
    user() {};
    user(string fname, string lname, string cteam, string pos, string stat, int age) 
    {
        setFirstName(fname);
        setLastName(lname);
        setCurrentTeam(cteam);
        setPosition(pos);
        setStatus(stat);
        setAge(age);
    } ;
    void setFirstName(string fname)
        {firstname = fname;}
    void setLastName(string lname)
        {lastname = lname;}
    void setCurrentTeam(string cteam)
        {currentteam = cteam;}
    void setPosition(string pos)
        {position = pos;}
    void setStatus(string stat)
        {status = stat;}
    void setAge(int _age)
        {age = _age;}

    string getFirstName()
        {return firstname ;}
    string getLastName()
        {return lastname ;}
    string getCurrentTeam()
        {return currentteam ;}
    string getPosition()
        {return position ;}
    string getStatus()
        {return status ;}
    int getAge()
        {return age ;}
};

user player[20] ;

int main()
{
    menu() ;



    cin.get() ;
    return 0 ;

}

void storeinfo()
{
    string firstname ;
    string lastname ;
    string currentteam ;
    string position;
    string status ;
    int age ;

    for (int i=0; i < 3; i++)
    {
        cout << "Enter First Name : " ; 
        cin >> firstname ;
        player[i].setFirstName(firstname) ;
        cout << "Enter Last Name : " ; 
        cin >> lastname ;
        player[i].setLastName(lastname) ;
        cout << "Enter Player's Age : " ; 
        cin >> age;
        player[i].setAge(age) ;
        cout << "Enter Current Team : " ; 
        cin >> currentteam ;
        player[i].setCurrentTeam(currentteam) ;
        cout << "Enter Position : " ; 
        cin >> position ;
        player[i].setPosition(position) ;
        cout << "Enter Status : " ; 
        cin >> status ;
        player[i].setStatus(status) ;

        cout << "\n\n\n" ;
    }

    /*cout << string(50, '\n');*/

    menu() ;

}

void showinfo()
{
    for (int i=0; i < 3; i++)
    {
        cout << "First Name : " << player[i].getFirstName() << "\n" << "Last Name : " << player[i].getLastName() <<
            "\n" << "Age : " << player[i].getAge() << "\n" << "Current Team : " << player[i].getCurrentTeam() << 
            "\n" << "Position : " << player[i].getPosition() << "\n" << "Status :  " << player[i].getStatus()  << "\n\n";
    }

    cin.get() ;

    menu() ;
}

void menu()
{
    cout << "\n MENU" << "\n" ;
    cout << "\n 1. Store Player Information" ;
    cout << "\n 2. Show Player Informaton" ;
    cout << "\n 0. Exit \n \n" ;

    string x =  "";
    cin >> x ;

    if (x=="a")
    { 
        storeinfo() ;
    }
    else if (x=="b")
    {
        showinfo() ;
    }
    else if (x=="c")
    {
        exit(0) ;
    }
    else
    {
        cout << "Invalid Choice" ;
        menu() ;
    }   
}

i have done a linear search algorithm and seems to be working but the output i am getting is not correct below is the code for both functions, thank you again

int linsearch(string val)
{
    for (int j=0; j < 3; j++)
    {
        if  (player[j].getLastName()==val)
        {
            return j;
        }
        else 
        {
            return 1;
        }
    }




void showinfo()
{
    string search;
    int found ;


    cout << "Please Enter The Player's Last Name : " ;
    cin >> search ;

    found=linsearch(search);

    if (found== 1)
    {
        cout << "\n There is no player called " << search ;
    }
    else
    {
        cout << "\n First Name : " << player[found].getFirstName() << "\n" << "Last Name : " << player[found].getLastName() <<
            "\n" << "Age : " << player[found].getAge() << "\n" << "Current Team : " << player[found].getCurrentTeam() << 
            "\n" << "Position : " << player[found].getPosition() << "\n" << "Status :  " << player[found].getStatus()  << "\n\n";
    }

    cin.get() ;

    menu() ;

}

Answer 1

if your dataset can get big, hashtables are a solution which comes to mind. Be sure to select a hashing-algorithm which has not many collisions for your task. There are " perfect hashing algorithms ", by the way - if "0 collisions at all times" is important you should have a look into that - collision-free, fast hashing tables will speed up things significantly

Answer 2

The standard solution for mapping a key (like the user's name) to a record of some kind is a map .

The stock std::map uses a balanced tree, which gives you O(log N) searching, which is usually good enough (and much better than linear), and also lets you iterate through the names in sorted order. This requires an ordered type, meaning user1 < user2 makes sense.

Alternatively, std::unordered_map uses a hash table, which gives you O(1) searching, but doesn't have any ordering. This requires a hashable type, meaning hash(user1) makes sense. It also requires C++11, or a C++03 implementation that has it as part of tr1 , or boost .

Which one is appropriate depends on your needs—but often, they're both just fine, and it's just a matter of whether you have a natural ordering or a natural hash function.

Besides being more efficient for both searching and deleting from the middle than a vector , list , or other collection that requires linear searches, it's also a lot simpler and more natural. For example, compare these two:

user find_by_name(vector<user> users, string name) {
    return find_if(users.begin(), users.end(), [](auto it) { it->name == name; });
}

user find_by_name(map<string, user> users, string name) {
    return map.find(name);
}

(And, if you don't have C++11 lambdas, the find_if is even worse.)

As for whether "a linear search… is efficient enough", that really depends on how large the collection is. If you're doing 1 search every few seconds through 100 users, just about anything is efficient enough. If you're doing thousands of searches through millions of users, it probably isn't. If you don't know enough to estimate, just try it and see. Profiling should almost always be the first step in any optimization question. However, in this case, given that map or unordered_map is simpler, easier to read, and more natural than vector or list in the first place, I don't think you need to bother with that.