Odtnhj

I have 2 classes A and B. I create objects which are then put into a multimap. I want to print the all the keys with their corresponding values. However, my attempt to do this was not so successfull as I could create an iterator. I would like to ask how can I use the equal_range() method to accomplish this. Thanks in advance!

#include "pch.h"
#include <iostream>
#include <map>
using namespace std;
class A 
 int key;
public:
 A(int k) 
 key = k;
 
 A(A ob) 
 key = ob.key;
 
 int getKey() 
 return key;
 
;
class B 
 string value;
public:
 B(string v) 
 value = v;
 
;
multimap <A, B> mp;
int main() 
 mp = 
 make_pair(A(1),B("Crime and punishment")),
 make_pair(A(1),B("The Idiot")),
 make_pair(A(1),B("Brothers' Karamazov")),
 make_pair(A(2),B("Andreshko")),
 make_pair(A(2),B("The Gerak family")),
 make_pair(A(3),B("The name of the rose")),
 make_pair(A(3),B("Baudolino"))
 ;
 for (auto ml = mp.begin(); ml != mp.end();ml++) 
 multimap<pair<int, string>, pair<int, string>>::iterator it;

 

You already have your loop, but let's use C++11 ranged-loop instead.

You are just missing an accessor for the value, so let's assume that you have it (getValue) and just access the iterator:

for (const auto& pair : mp) 
 std::cout << ml.first.getKey() << "t" << ml.second.getValue() << std::endl;

Also change this:

A(A ob)

To

A(const A& ob)

This will give a real copy assignment. But the default copy constructor is also fine, so don't mention it at all, the default one is already good for you.

Some things you need:

• Getter methods for class B.


• A less than operator for your key class A.


• A copy constructor for class A.

In the code below if remove code not needed (but would be nice to keep in live code) to show what is really used.

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

using namespace std;

class A 
 int key;
public:
 A(int k) : key(k)
 A(A const& ob) : key(ob.key) 
 A& operator=(A const& ob) = delete;
 int getKey() const return key; 
 friend bool operator<(A const&left, A const&right) return left.key < right.key; 
;

class B 
 string value;
public:
 B(string const& v) : value(v) 
 B(B const&) = default;
 B& operator=(B const&) = delete;
 string const& getValue() const return value; 
;

multimap<A, B> mp;

int main() 
 mp = 
 make_pair(A(3), B("Baudolino")),
 make_pair(A(1), B("Crime and punishment")),
 make_pair(A(1), B("Brothers' Karamazov")),
 make_pair(A(2), B("Andreshko")),
 make_pair(A(1), B("The Idiot")),
 make_pair(A(2), B("The Gerak family")),
 make_pair(A(3), B("The name of the rose"))
 ;
 for (auto const & item : mp) 
 cout << "key:" << item.first.getKey() << " value:"" << item.second.getValue() << ""n";