function validBraces checks if string contains valid sequence of braces

Braces.hpp

#include <string>
// #include <algorithm>
// #include <iostream>
#include <vector>
#include <map>
#include <stack>

// #pragma once

#ifndef BRACES_H
#define BRACES_H

bool validBracesSequence(const std::string&);	

// gets any string with braces
bool validBraces(const std::string& someString) {
	// checks if character is a bracket
	auto isBrace = [](char c) {
		for (const auto& b : "()[]{}<>") {
			if (c == b) {
				return true;
			}
		}
		return false;
	};

	std::string braces;
	
	// copying only braces from string	
	for (const auto& sym : someString) {
		if (isBrace(sym)) {
			braces += sym;
		}
	}

	return validBracesSequence(braces);
}

// STRING MUST CONTAIN ONLY SYMBOLS (){}[]<>
bool validBracesSequence(const std::string& braces) {
	const std::map<char, char> pairs = {
		{'(', ')'},
		{'[', ']'},
		{'{', '}'},
		{'<', '>'}
	};
	// keys for map pairs
	const std::vector<char> leftBraces = { '(', '[', '{', '<' };
	
	std::stack<char> seq;

	for (const auto& c : braces) {
		if (count(leftBraces.begin(), leftBraces.end(), c)) {
			seq.push(pairs[c]);
		} else if (c == seq.top()) {
			seq.pop();
		} 
		else if (seq.empty() || c != seq.top()) {
			return false;
		}
	}
	// after all stack must be empty
	return seq.empty();
}

#endif