Sorting a std::map by value before output & destroy

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天涯浪人 2020-12-01 11:30

I\'m aware that map is not prepared to be sorted. It\'s heavily optimized for fast and random key access and actually doesn\'t support std::sort.

My cur

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孤街浪徒 (楼主)

2020-12-01 11:58

May not be the most elegant way, but you can sort them via value in a set as:

#include 
#include 
#include 
#include 

using namespace std;

struct sortPairSecond
{
   bool operator()(const pair &lhs, const pair &rhs)
   {
       return lhs.second < rhs.second;
   }
};


int main (int argc, char *argv[])
{
    cout << "Started...\n";
    map myMap;
    myMap["One"]   = 1;
    myMap["Ten"]   = 10;
    myMap["Five"]  = 5;
    myMap["Zero"]  = 0;
    myMap["Eight"] = 8;


    cout << "Map Order:\n---------------\n";
    set, sortPairSecond > mySet;
    for(map::const_iterator it = myMap.begin(); it != myMap.end(); ++it)
    {
        cout << it->first << " = " << it->second << "\n";
        mySet.insert(*it);
    }

    cout << "\nSet Order:\n--------------\n";
    for(set >::const_iterator it = mySet.begin(); it != mySet.end(); ++it)
    {
        cout << it->first << " = " << it->second << "\n";
    }

    return 1;
}

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