kurrerc

#include <iostream>
#include <vector>
#include <string>
#include <list>
#include <sstream>

std::vector<int> readInput() {
	std::vector<int> vec;
	std::string line;
	getline(std::cin, line);
	std::istringstream istr(line);
	int number;
	while (istr >> number) {
		vec.push_back(number);
	}
	return vec;
}

void handleTrainOne(std::vector<int>& trainTwo, std::list<int>& mergeTrains, std::string& letterSequence) {
	int element = trainTwo.back();
	mergeTrains.push_front(element);
	letterSequence.push_back('B');
	trainTwo.pop_back();
}

void handleTrainTwo(std::vector<int>& trainOne, std::list<int>& mergeTrains, std::string& letterSequence) {
	int element = trainOne.back();
	mergeTrains.push_front(element);
	letterSequence.push_back('A');
	trainOne.pop_back();
}

void handleBothTrains(std::vector<int>& trainOne, std::vector<int>& trainTwo, std::list<int>& mergeTrains,
	std::string& letterSequence) {

	int trainOneElement = trainOne.back();
	int trainTwoElement = trainTwo.back();

	if (trainOneElement < trainTwoElement) {
		mergeTrains.push_front(trainOneElement);
		letterSequence.push_back('A');
		trainOne.pop_back();
	}
	else {
		mergeTrains.push_front(trainTwoElement);
		letterSequence.push_back('B');
		trainTwo.pop_back();
	}

}

void mergedTrains(std::vector<int>& trainOne, std::vector<int>& trainTwo,
				std::list<int>& mergeTrains, std::string& letterSequence) {

	while (true) {

		const bool trainOneEmpty = trainOne.empty();
		const bool trainTwoEmpty = trainTwo.empty();

		if (trainOneEmpty && trainTwoEmpty) {
			break;
			continue;
		}

		if (trainOneEmpty) {
			handleTrainOne(trainTwo, mergeTrains, letterSequence);
			continue;
		}

		if (trainTwoEmpty) {
			handleTrainTwo(trainOne, mergeTrains, letterSequence);
			continue;
		}

		handleBothTrains(trainOne, trainTwo, mergeTrains, letterSequence);
	}
}

void printSolution(std::list<int>& mergeTrains, std::string& letterSequence) {
	std::cout << letterSequence << std::endl;

	for (int num : mergeTrains) {
		std::cout << num << ' ';
	}
}


int main() {

	std::vector<int> trainOne = readInput();
	std::vector<int> trainTwo = readInput();
	std::list<int> mergeTrains;
	std::string letterSequence;

	mergedTrains(trainOne, trainTwo, mergeTrains, letterSequence);
	printSolution(mergeTrains, letterSequence);
}