Comparing two multimap objects in c++

Question

i need to compare two multimap objects to find out whether they are equal or not

i know by using std::equal we can compare two vector object equality but is it possible to use this algorithm for comparing to multimap objects?

typedef std::multimap<std::string, std::string> HeaderMap;
HeaderMap _map,_secMap;


_map.insert(HeaderMap::value_type("A", "a"));
_map.insert(HeaderMap::value_type("B", "b"));

_secMap.insert(HeaderMap::value_type("A", "a"));
_secMap.insert(HeaderMap::value_type("B", "b"));



**std::equal(_map.begin(),_map.end(),_secMap.begin()); // is this true?**

if above code snippet is not true, how i can compare two multimap objects?(i don't ant to iterate objects and compare keys and values one by one) thanks

You want us to run your code for you and tell you the result? — Fiktik, Mar 25 '13 at 09:41
Possible duplicate of http://stackoverflow.com/questions/8559820/compare-two-multimaps-c — Jonathan Potter, Mar 25 '13 at 09:42
FikTik :> no only suggest me a way that i use it to compare to multimap objects.if their content are equal return true else return flase. — Benyamin Jane, Mar 25 '13 at 09:45

juanchopanza · Accepted Answer · 2013-03-25T10:14:56.447

You can compare them with operator==:

map_ == secMap_;

This will internally compare elements one by one until the first unequal one is found. There is no way of avoiding that. Here is a working example:

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

int main()
{
  typedef std::multimap<std::string, std::string> HeaderMap;

  HeaderMap m1, m2, m3;

  m1.insert(HeaderMap::value_type("A", "a"));
  m1.insert(HeaderMap::value_type("B", "b"));

  m2.insert(HeaderMap::value_type("A", "a"));
  m2.insert(HeaderMap::value_type("B", "b"));

  m3.insert(HeaderMap::value_type("A", "a"));
  m3.insert(HeaderMap::value_type("B", "b"));
  m3.insert(HeaderMap::value_type("C", "c"));


  std::cout << std::boolalpha;
  std::cout << (m1==m2) << " " << (m1==m3) << std::endl;    
}

Output:

true false

Bear in mind that names with leading underscores are reserved for the implementation so you should not use them.

Comparing two multimap objects in c++

1 Answers1