Challenge: Take input from a user and print the lowest number possible using the digits from the given input.

IntegerSort.cpp

#include <iostream> // Needed for std::cout/cin
#include <vector> // Needed for std::vector
#include <string> // Needed for std::string
#include <algorithm> // Needed for std::sort

int main()
{
	std::string user_input;
	std::vector<int> digits;
	bool negative;

	std::cout << "Enter an Integer: ";
	std::cin >> user_input;

	negative = (user_input[0] == '-') ? true : false;


	/* We cast to an int before sorting so it sorts the decimal equivilent
		then we throw it back to a char before we print. */
	for (std::string::iterator x = user_input.begin(); x != user_input.end(); ++x)
		/* This will stop all the non-number characters from printing. */
		if (static_cast<int>(*x) >= 48 && static_cast<int>(*x) <= 57)
        		digits.push_back(static_cast<int>(*x));

	if (negative)
	{
		/* We have to do a reverse sort for negatives. */
		std::sort(digits.rbegin(), digits.rend());
		/* Since we don't print anything but numbers later
			we have to print this ahead of time. */
		std::cout << "-";
	}
	else
	{
		std::sort(digits.begin(), digits.end));
	}

	for (std::vector<int>::iterator x = digits.begin(); x < digits.end(); ++x)
		std::cout << static_cast<char>(*x);

	std::cout << std::endl;

	return 0;
}