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Generate Random numbers uniformly over entire range

I want to generate the random number in c++ with in some range let say i want to have number between 25 and 63.

How can I have that?

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6 Answers

Since nobody posted the modern C++ approach yet,

#include <iostream> #include <random> int main() { std::random_device rd; // obtain a random number from hardware std::mt19937 gen(rd()); // seed the generator std::uniform_int_distribution<> distr(25, 63); // define the range for(int n=0; n<40; ++n) std::cout << distr(gen) << ' '; // generate numbers }
8

You can use the random functionality included within the additions to the standard library (TR1). Or you can use the same old technique that works in plain C:

25 + ( std::rand() % ( 63 - 25 + 1 ) )
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int range = max - min + 1; int num = rand() % range + min;
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int random(int min, int max) //range : [min, max] { static bool first = true; if (first) { srand( time(NULL) ); //seeding for the first time only! first = false; } return min + rand() % (( max + 1 ) - min); }
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Use the rand function:

Quote:

A typical way to generate pseudo-random numbers in a determined range using rand is to use the modulo of the returned value by the range span and add the initial value of the range: ( value % 100 ) is in the range 0 to 99 ( value % 100 + 1 ) is in the range 1 to 100 ( value % 30 + 1985 ) is in the range 1985 to 2014
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float RandomFloat(float min, float max) { float r = (float)rand() / (float)RAND_MAX; return min + r * (max - min); }
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