#include <string>
#include <vector>
#include <cctype>
#include <iostream>
#include <algorithm>
#include <unordered_map>

class Solution {
public:
	static std::string mostCommonWord(std::string paragraph, const std::vector<std::string>& banned) {
		std::unordered_map<std::string, int> freq;
		std::for_each(paragraph.begin(), paragraph.end(), [](char& c){ c = std::tolower(c); });
		paragraph.push_back('.');
		const char* ptr = paragraph.c_str();
		for (const char* p1 = ptr, * p2 = ptr; *p2; ++p2) {
			if (!std::isalpha(*p2)) {
				if (p2 - p1)
					++freq[std::string(p1, p2)];
				p1 = 1 + p2;
			}
		}
		std::for_each(banned.cbegin(), banned.cend(), [&freq](const std::string& str) { freq.erase(str); });
		return std::max_element(freq.cbegin(), freq.cend(), [](const std::pair<std::string, int>& x, const std::pair<std::string, int>& y) { return x.second < y.second; })->first;
	}
};

int main() {
	std::cout << Solution::mostCommonWord("Bob hit a ball, the hit BALL flew far after it was hit.", {"hit"});
}