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Original post by Null and Void
ZealousElixir, your version only finds a point on the outside of the circle (not any point within the circle).

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Also, yours will be less random due to your use of the low order bits (you're using modulo instead of division to cap the random value).

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Beer Hunter, what I mean was: what if every x returned is 0 and every 0 returned is 0? The point 0,0 isn't going to be in the circle. Well, that isn't very likely, I know. But, there's someodd other points that aren't in the circle either. So, what if every other value is rejected because of that? The algorithm could take a very long time to finally pick a point inside the circle if you're unlucky. If you're really unlucky, the algorithm could never complete!

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    #include <stdlib.h>#include <time.h>#include <math.h>#define PIOVER180 (3.14156/180)...time_t t; srand((unsigned int)time(&t));...float angle = float(rand()%360);float radius = 5; //whatever.float randradius = rand()%radius;float x = float(sin(angle*PIOVER180) * randradius);float y = float(cos(angle*PIOVER180) * randradius);...    

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In Numerical Recipes in C: The Art of Scientific Computing ( William H. Press, Brian P. Flannery, Saul A. Teukolsky,W illiam T. Vetterling; New York: Cambridge University Press, 1992 (2nd ed., p. 277)), the following comments are made:

"If you want to generate a random integer between 1 and 10, you should always do it by using high-order bits, as in
j=1+(int)(10.0*rand()/(RAND_MAX+1.0));
and never by anything resembling
j=1+(rand() % 10);
(which uses lower-order bits)."

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0 occurs 9 times1 occurs 9 times2 occurs 9 times3 occurs 9 times4 occurs 9 times5 occurs 9 times6 occurs 9 times7 occurs 9 times8 occurs 9 times9 occurs 9 times10 occurs 9 times11 occurs 9 times12 occurs 9 times13 occurs 9 times14 occurs 9 times15 occurs 9 times16 occurs 8 times17 occurs 8 times18 occurs 8 times19 occurs 8 times20 occurs 8 times21 occurs 8 times22 occurs 8 times23 occurs 8 times24 occurs 8 times25 occurs 8 times26 occurs 8 times27 occurs 8 times28 occurs 8 times29 occurs 8 times

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Original post by Anonymous Poster
The angle and radius way is very bad, you get higher point density near the center.

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// Generate a random number between min and maxtemplate T Random(const T min, const T max){    return min + T ( double(rand()) * double(max-min) / double(RAND_MAX) );}