The number of elements can be counted by using map. The following three methods are mainly introduced:

1. Use find function to count the times of each element

void test_map2()
{
	string strs[] = { "Apple", "Banana", "Strawberry", "Apple", "Banana", "Banana", "Banana", "Apple", "Banana", "Strawberry" };
	map<string, int> countmap;
	//Using find to count the number of occurrences of each element
	for (const auto& e : strs)
	{
		map<string, int>::iterator it = countmap.find(e);
		//countmap.end() is the next element of the last element in the map
		if (it != countmap.end())
		{
			//If found, value + +;
			it->second++;
		}
		else
		{
			//If you don't insert it again, you have to traverse it again. It's a little redundant
			countmap.insert(make_pair(e, 1));
		}
	}
	//Traverse each element
	map<string, int>::iterator cit = countmap.begin();
	while (cit != countmap.end())
	{
		cout << cit->first << ":" << cit->second << endl;
		cit++;
	}
}

2. Use insert to count the times of each element

void test_map3()
{
	string strs[] = { "Apple", "Banana", "Strawberry", "Apple", "Banana", "Banana", "Banana", "Apple", "Banana", "Strawberry" };
	map<string, int> countmap;
	//pair<iterator,bool> insert (const value_type& val);
	//The return value of this type of insert is a pair, the first element is an iterator, pointing to the map of the newly inserted element, and the second element is a bool value. If the insert succeeds, true will be returned, otherwise false will be returned
	for (const auto& e : strs)
	{
		std::pair<std::map<std::string, int>::iterator, bool> ret = countmap.insert(make_pair(e, 1));
		if (ret.second == false)
		{
			ret.first->second++;
		}
	}
	map<string, int>::iterator cit = countmap.begin();
	while (cit != countmap.end())
	{
		cout << cit->first << ":" << cit->second << endl;
		cit++;
	}
}

3. Use operator [] to count the number of occurrences of each element

void test_map4()
{
	string strs[] = { "Apple", "Banana", "Strawberry", "Apple", "Banana", "Banana", "Banana", "Apple", "Banana", "Strawberry" };
	map<string, int> countmap;
	for (const auto& e : strs)
	{
		//Call operator []; then + + the return value.
		countmap[e]++;
	}
	for (auto& e : countmap)
	{
		cout << e.first << ":" << e.second << endl;
	}
}

Output results of the above three methods:

If you don't understand how to count the times with operator [], please refer to the blog https://blog.csdn.net/yam_sunshine/article/details/89930311

It details the usage and principle of operator [].