#include <iostream>
#include <map>
#include <string>
#include <iterator>
#include <vector>
#include <functional>


/*
 * Generic implementation to erase elements by Callback
 * It iterates over all the elements and for every element it executes
 * the callback, if it returns the true then it will delete
 * that entry and move to next.
 */
template<typename K, typename V>
int erase_if(std::map<K, V> & mapOfElemen, bool(* functor)(V))
{
	bool totalDeletedElements = 0;
	auto it = mapOfElemen.begin();
	// Iterate through the map
	while(it != mapOfElemen.end())
	{
		// Check if value of this entry matches with given value
		if(functor(it->second))
		{
			totalDeletedElements++;
			// Erase the current element, erase() will return the
			// next iterator. So, don't need to increment
			it = mapOfElemen.erase(it);
		}
		else
		{
			// Go to next entry in map
			it++;
		}
	}
	return totalDeletedElements;
}

bool isODD(int val)
{
	if(val % 2 == 1)
			return true;
		else
			return false;
}
int main() {

	// Map of string & int i.e. words as key & there
	// occurrence count as values
	std::map<std::string, int> wordMap = {
				{ "is", 6 },
				{ "the", 5 },
				{ "hat", 9 },
				{ "at", 6 }
			};

	std::cout << "Map Entries Before Deletion" << std::endl;
	// Print the map elements
	for (auto elem : wordMap)
		std::cout << elem.first << " :: " << elem.second << std::endl;

	// Erase all the elements whose value is ODD
	int deletedCount = erase_if(wordMap, &isODD);

	std::cout<<"Total elements deleted = "<<deletedCount<<std::endl;

	std::cout << "Map Entries After Deletion" << std::endl;
	// Print the map elements
	for (auto elem : wordMap)
		std::cout << elem.first << " :: " << elem.second << std::endl;


	return 0;
}