int posX = (rand() % 30) + 1;
Really quick rand() question
Author
Hey guys,
Just trying to figure out if this is possible
I'm trying to generate a random number between -30 and 30. How would I go about doing this. I know the code to get one for a number between 0 and 30:
But what can I add to this line to make the beginning of the range -30?
Many thanks
Your code generates a number in the range 0..30. Your new requirement is a range of 60, so you generate a number between 0..60. You can then offset the range by adding or subtracting a number from the range, moving the values in the range to
0 + N..60 + N.
0 + N..60 + N.
Your code will get a number between 0 and 31. We take the remainder (modulus) when divided by 30. This is in the range 0 to 29 (between -1 and 30). We then add one and are in the range 1 to 30 (between 0 and 31).
To get between -30 and 30 (-29 to 29) we see that there is a total 59 different values so we get a in the range from 0 to 58 and subtract 29.
To get between -30 and 30 (-29 to 29) we see that there is a total 59 different values so we get a in the range from 0 to 58 and subtract 29.
int posX = (rand()%59)-29;
Author
Ah thanks guys, I did think of doing that, but thought there might be a way of setting up what the first number in the range is
But thats good enough for me, :)
But thats good enough for me, :)
If you want a way to simply set the low and high bounds, just do something like this:
int Random(int low, int high)
{
return low + rand()%(high-low+1);
}
int Random(int low, int high)
{
return low + rand()%(high-low+1);
}
Quote:Original post by Kuro
If you want a way to simply set the low and high bounds, just do something like this:
int Random(int low, int high)
{
return low + rand()%(high-low+1);
}
Ive heard that something like this is better ( something about the low order bits being less random than the higher order ones with rand() ):
return low + int(( rand() / float(RAND_MAX) ) * (high - low + 1) );
Hope I got the math right =/
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