How to enter info into a map

[Ch1156]

I'm trying to get familiar with maps, so im making a program that enters names and ages and puts them into a map but I dont know how to actually set them in the map since it takes 2 values.

#include <iostream>
#include <map>
#include <string>

using namespace std;

int main()
{
    map<string, int> newMap;

    int nameCount = 5;
    string name = "default";
    int age = 0;

    for(int i = 0; i < 5; i++)
    {
        cout << "Enter " << nameCount << " names and ages." << endl;
        cout << "Name: ";
        getline(cin, name);
        newMap?????
        cout << "Age: ";
        cin >> age;
        newMap?????
        
        nameCount--;
    }

    return 0;
}

[Repeater]

You insert pair objects into the map.

std::pair<string, int> in this case, as the map is a map<string, int>

To create a pair object, you can specify the kind of pair yourself to insert, which would be something like:
newMap.insert ( std::pair<string,int>(std::string("Beans"),1) );

or use the std::make_pair function, something like this:
newmap.insert(std::make_pair("Beans",1));

[Ch1156]

Great, thank you, I got it working. I have one question though about something unrelated to map, in my for loop, I had a getline, and after it would get the first name and age it would then skip thge name and get the age and screw up, why is that? I changed it to a cin >> and it works fine now. How would I use getline in the for loop?

#include <iostream>
#include <map>
#include <string>

using namespace std;

int main()
{
    map<string, int> newMap;

    int nameCount = 5;
    string name = "default";
    int age = 0;

    for(int i = 0; i < 5; i++)
    {
        cout << "Enter " << nameCount << " names and ages." << endl;
        cout << "Name: ";
        cin >> name;
        cout << "Age: ";
        cin >> age;
        newMap.insert(pair<string, int>(name, age));

        nameCount--;
    }

    cout << "\n\n" << endl;

    for(map<string, int>::iterator it = newMap.begin(); it != newMap.end(); it++)
    {
        cout << "Name: " << it->first << " Age: " << it->second << endl;
    }

    return 0;
}

[Handy Andy]

Hello Ch1156,

As you said a map takes two values, so line 20 should not be there until you have both "name" and "age" to put into the map.

The easiest way to add to a map is:

newMap[name] = age;

which would be done on line 23.

Line 17 I would put above the for loop and replace the variable "nameCount" with 5.

Change line 17 something like this:
std::cout << "Enter name " << i + 1 << ": ";
and maybe something similar for line 21. And about line 25 print a blank line.

After this "nameCount" would no longer have any use.

These may help with the maps:
http://www.cplusplus.com/reference/map/map/
http://www.cplusplus.com/reference/map/map/map/

Second link has an example of how to put information into a map. Just one of a couple ways.

Hope that helps,

Andy

[Handy Andy]

Hello Ch1156,

After the cin >> age; the next line needs to be:
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); // <--- Requires heder file <limits>.

Andy

[JLBorges]

#include <iostream>
#include <map>
#include <string>

int main()
{
    std::map< std::string, int > name_age_map;

    std::string name ;
    int age = 0;

    for(int i = 0; i < 5; i++)
    {
        std::cout << "Name: ";
        std::getline( std::cin, name ) ; // unformatted input

        std::cout << "Age: ";
        std::cin >> age ; // formatted input
        // formatted input leaves trailing white space (typically a new line)
        // in the input buffer. extract it and throw it away. otherwise
        // the unformatted input (for name), which does not skip leading white space
        // would read only up to the new line remaining in the input buffer
        std::cin.ignore( 1000, '\n' ) ;

        // it is more efficient (and, in this case, less verbose) to construct the string in-place
        // within the map. however, if the name is already present in the map, the age would not be
        // updated. we can check for this; but in this simple example the check is omitted
        name_age_map.emplace( name, age );
    }

    std::cout << "\n\n\n" ;

    // classical for loop: simpler to let the compiler deduce the type of the iterator
    // that way, the code is more readable and more maintenance-free
    for( auto it = name_age_map.begin(); it != name_age_map.end(); ++it )
    {
        std::cout << "Name: " << it->first << " Age: " << it->second << '\n';
    }

    // simplest: in general favour a range-based loop over a classical for loop
    for( const auto& pair : name_age_map )
    {
        std::cout << "Name: " << pair.first << " Age: " << pair.second << '\n';
    }
}