Preventing the subtraction of two random integers from equaling a negative integer? - c++

Question

Simple mathgame.cpp.
case(2) is the subtraction of two random integers, but the **results cant be less than 0.
** I need 'subOp' to only hold the values of 'ranNum1' - 'ranNum2' when they equal >= 0
#include <iostream>
#include <ctime>
#include <cstdlib>
#include <string>
using namespace std;
int main()
{
// Initialize random number generator.
srand(time(0));
// Declares variable as a random integer between 0-12
// int ranNum1 = rand() % 13;
// int ranNum2 = rand() % 13;
int menuChoice = 0;
int userAns=0;
// String variable for the game menu
string mathMenu =
"\n\n\tMATH GAME SELECTION\n\t-------------------\n\t1) Addition\n"
"\t2) Subtraction\n\t3) Multiplication\n\t4) -EXIT-\n";
// Answer responses
string cAns = "\n\tCORRECT ANSWER!" , wAns = "\n\tWRONG ANSWER!";
// While the user doesnt request to exit...
while (menuChoice != 4)
{
int ranNum1 = rand() % 13;
int ranNum2 = rand() % 13;
switch (menuChoice)
{
case (0):
break;
case (1): { int addOp = ranNum1 + ranNum2;
cout << "\tWhat is " << ranNum1 << " + " << ranNum2 << " = [?]\n \tYour answer: ";
cin >> userAns;
if (userAns == addOp) {
cout << cAns; }
else{
cout << wAns << "\n\tThe correct answer was " << addOp; }
break; }
case (2): { int subOp = ranNum1 - ranNum2;
do {
cout << "\tWhat is " << ranNum1 << " - " << ranNum2 << " = [?]\n\tYour answer: ";
cin >> userAns;
if (userAns == subOp) {
cout << cAns;
}
else {
cout << wAns << "\n\tThe correct answer was " << subOp;
}
} while (subOp < 0);
break; }
case (3):{ int multOp = ranNum1 * ranNum2;
cout << "\tWhat is " << ranNum1 << " x " << ranNum2 << " = [?]\n \tYour answer: ";
cin >> userAns;
if (userAns == multOp) {
cout << cAns; }
else {
cout << wAns << "\n\tThe correct answer was " << multOp; }
break; }
//Error message/ validator for integers between 1-4.
default: cout << "\t**Invalid menu selection** \n\a";
}
//Error message/ validator for input other than integer.
cout << mathMenu << endl << " Please Select An Option (1-4): ";
while (!(cin >> menuChoice)) {
cin.clear();
cin.ignore(1000, '\n');
cout << "Please ONLY select the given options (1-4): \a";
}
cout << endl;
}
system("pause");
return 0;
}
I've tried several different loops and bools. How do I loop through the equation until the results will only equal >0?

Answer 1

You can make a conditional statement to check whether the second value is greater than the first one. If so, then swap between them.
if (ranNum1 < ranNum2)
std::swap(ranNum1, ranNum2);
int subOp = ranNum1 - ranNum2;
Now, the value of ranNum1 is always greater than ranNum2.