A console based number guessing game

GuessNumber.cpp

// NumberGuessing.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <ctime>
#include <vector>
#include <numeric>
#include <limits>
#include <string>
#include <cassert>

// Number guessing game that shows your progress
class GuessNumber {
private:
	int limit = 20; // default limit
	std::vector<int> values;
	int ans, valuesLeft;
	bool queried;
public:
	GuessNumber(bool defaultLimit) {
		std::srand(static_cast<unsigned>(std::time(nullptr)));
		reset(defaultLimit);
	}
	GuessNumber() : GuessNumber(false) {
	}

	// contains main program
	void start();
private:
	
	// returns true if choice == ans
	bool validateAnswer(int choice);
	// resets state variables
	void reset(bool = true);
	// asks user to restart (optionally asks user for limit)
	bool queryRestart();
	// gives a random number within a range
	int randomRange(unsigned min, unsigned max) {
		return min + (rand() % (int)(max - min + 1));
	}
	// let's user know if choice is greater than or less than ans
	void printSelectionMessage(int choice);
};

void GuessNumber::reset(bool defaultLimit) {
	if (!defaultLimit) {
		system("cls");
		std::cout << "# of choices: ";
		assert(std::cin >> limit);
	}
	queried = false;
	values.resize(limit);
	valuesLeft = values.size();
	std::iota(values.begin(), values.end(), 1);
	ans = randomRange(1, limit);
}

void GuessNumber::start() {
	int choice = 0;
	while (true) {
		// new line before the program end message
		std::cout.put('\n');
		// check for a valid answer (so we can either end the game or reset state
		// (for a restart) before anything else is done.
		if (validateAnswer(choice)) {
			// if the user wants to restart, reset state
			// otherwise break from the loop
			if (queryRestart()) {
				// after state is cleared, game will resume as normal
				reset(false);
			}
			else {
				// break from this loop if user doesn't restart
				break;
			}
		}

		// clear screen each frame
		system("cls");

		// state data
		if (queried) {
			printSelectionMessage(choice);
		}
		else {
			// new line before the values
			std::cout.put('\n');
		}

		bool oneChoiceLeft = false;
		// loop through the values and update available numbers
		for (int i = 0; i < limit; ++i) {
			if (queried) {
				if (values[i] != -1) {
					// mark the numbers greater than or equal to (if choice > ans) or
					// less than or equal to (if choice < ans) as removed
					if ((choice < ans && i+1 <= choice) || (choice > ans && i+1 >= choice)) {
						values[i] = -1;
						valuesLeft--; // decrement number of available choices
					}
				}
			}

			// print the values (X for removed)
			if (values[i] == -1) 
				std::cout << "X ";
			else
				std::cout << values[i] << ' ';

			// If there's one choice left set a flag that the
			// answer should be given immediately
			if (valuesLeft == 1) {
				oneChoiceLeft = true;
				// rather than breaking, let the loop finish
				// so that all values are written out.
			}
		}

		// one choice left, so display answer
		if (oneChoiceLeft) continue;

		std::cout << "\nChoose your number (" << valuesLeft << " left): ";
		std::cin >> choice;
		// a valid answer is one that is within the limit ({1,..,limit})
		queried = (choice >= 1 && choice <= limit);
	}
	std::cout << "Thank you for playing. Press any key to exit.\n";
	std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
	std::cin.get();
}

bool GuessNumber::validateAnswer(int choice) {
	if (queried) {
		if (valuesLeft == 1) {
			std::cout << "\nGAME OVER. Answer: " << ans << '\n';
			return true;
		}
		else if (choice == ans) {
			std::cout << "You got it, the answer is " << choice << '\n';
			return true;
		}
	}
	return false;
}

void GuessNumber::printSelectionMessage(int choice) {
	std::cout << "The answer is ";
	if (ans < choice) std::cout << "less ";
	if (ans > choice) std::cout << "greater ";
	std::cout << "than " << choice << "\n";
}

bool GuessNumber::queryRestart() {
	std::cout << "restart: r\nquit: q\n";
	char c;
	if (std::cin >> c && c == 'r') {
		return true;
	}
	return false;
}

int main()
{
	GuessNumber game;
	game.start();
}