Random #'s in C++
December 16, 2002 07:51 PM
Does anyone know where I can find a tutorial about generating random numbers in C++?
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122
December 16, 2002 08:57 PM
include "time.h"
then you have to seed it, to make it a differnet random every time by this syntax...
float sec;
time(&sec);
srand(sec);
from this point, you make calls to rand(), which returns a value between 0-1. To make it a larger number you could say things like...
int num = rand()%18; //gives random number between 0 and 18 (not including 18)
hope i helped ya out
then you have to seed it, to make it a differnet random every time by this syntax...
float sec;
time(&sec);
srand(sec);
from this point, you make calls to rand(), which returns a value between 0-1. To make it a larger number you could say things like...
int num = rand()%18; //gives random number between 0 and 18 (not including 18)
hope i helped ya out
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December 16, 2002 09:03 PM
srand((unsigned)time(0)); to seed.
and rand() returns a number between 0 and RAND_MAX, inclusive.
and both srand and rand are from the C standard library, not C++. there is the STL''s random_shuffle, but it might not be what you want.
and rand() returns a number between 0 and RAND_MAX, inclusive.
and both srand and rand are from the C standard library, not C++. there is the STL''s random_shuffle, but it might not be what you want.
1,298
December 16, 2002 09:23 PM
int RandomInt(int min, int max) { if(min>max) return RandomInt(max, min); else return std::rand()%(max-min+1)+min; } float RandomFloat(float min, float max) { return std::rand()*(max-min)/static_cast<float>(RAND_MAX)+min; } [edited by - smart_idiot on December 16, 2002 10:24:07 PM]
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278
December 17, 2002 03:05 AM
Yes but what if you need 30 random numbers all in the same millisecond? Putting the same time into the equation should always return the same random number right?
~Vendayan
~Vendayan
"Never have a battle of wits with an unarmed man. He will surely attempt to disarm you as well"~Vendayan
122
December 17, 2002 03:11 AM
const SHNUM = max #;
int picknum()
{
int number;
number = (rand() % SHNUM);
return(number);
}
then to actually put it use, for example I''ll store the random # in a variable, so it could be used for like a number guessing game or something:
srand((unsigned)time(NULL));
int theNumber = picknum() + 1;
this makes the variable theNumber store a random number between 1, and whatever number you used for SHNUM
int picknum()
{
int number;
number = (rand() % SHNUM);
return(number);
}
then to actually put it use, for example I''ll store the random # in a variable, so it could be used for like a number guessing game or something:
srand((unsigned)time(NULL));
int theNumber = picknum() + 1;
this makes the variable theNumber store a random number between 1, and whatever number you used for SHNUM
"You probably use those fat crayons made for retarded kids." - warbux
December 17, 2002 03:11 AM
you only need to seed with srand at the begining of the program, that way each time it is run you will get different numbers
278
December 17, 2002 03:20 AM
how exactly does that work?
~Vendayan
~Vendayan
"Never have a battle of wits with an unarmed man. He will surely attempt to disarm you as well"~Vendayan
1,047
December 17, 2002 03:25 AM
int seed = 0;void srand(int value) { seed = value;}int rand() { return seed++;}srand((int)time(NULL));for(int i=0;i<100;++i) { std::cout<<"random value: "<<rand()<<std::endl;} this rand() is overly simplified, but i think you get the idea..
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[edited by - davepermen on December 17, 2002 4:26:16 AM]
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