Question

i have a qt form that has a multiplication problem and 4 buttons. the 4 buttons (choices) are randomly generated and so is the question.

i just want to randomize the 4 choices so they are random but none of them are equivalent to the other choices. this is how i am doing it right now, but it’s not working very well:

while (choice1 == choice2 || choice1 == choice3 || choice1 == choice4)
    choice1 = (rand() % max) + 1;
while (choice2 == choice1 || choice2 == choice3 || choice2 == choice4)
    choice2 = (rand() % max) + 1;
while (choice3 == choice1 || choice3 == choice2 || choice3 == choice4)
    choice3 = (rand() % max) + 1;
while (choice4 == choice1 || choice4 == choice2 || choice4 == choice3)
    choice4 = (rand() % max) + 1;

does anyone else have a better way?

Answer 1

Since the number of elements is fixed and very small, your overall approach is pretty reasonable. However, the implementation is buggy.

Here is how it can be fixed:

choice1 = (rand() % max) + 1;
do { choice2 = (rand() % max) + 1; } while (choice2 == choice1);
do { choice3 = (rand() % max) + 1; } while (choice3 == choice1 || choice3 == choice2);
do { choice4 = (rand() % max) + 1; } while (choice4 == choice1 || choice4 == choice2 || choice4 == choice3);

There are better ways to do this if one needs a larger number of elements, or if the number of elements is variable.