Getting the minimum element of a map<>.

min_element_of_map.cpp

#include <map>
#include <string>
#include <algorithm>
#include <iostream>
using namespace std;

int main(int argc, const char* argv[])
{
        // hint: ternary operator ? :
        string const text =
                argc == 2
                        ? argv[1]
                        : "Hello bello, mello yellow";

        map<char, unsigned> freq;
        for (char c : text)
                ++freq[c];
        
        auto isLess = [](const auto& a, const auto& b) -> bool {
                return a.second < b.second;
        }
        auto k = min_element(begin(freq), end(freq), isLess);

        auto i = min_element(begin(freq), end(freq), [](const auto& a, const auto& b) -> bool {
                return a.second < b.second;
        });

        if (i != end(freq))
                cout << "Minimum element: " << i->first << " with count " << i->second << '\n';
        else
                cout << "No minimum found.\n";
}

Thank you!