CareerCup

Use shiftxor algorithm to generate a random number:

#include "CommonHeader.h"

// Generate RNG numbers.
// The below initialises the seed to pre-determined number
// To get a TRNG (True-Random-Number-Generator) one should initialise the 
// seed with a true random number (e.g. capture the mouse current point and use it as the seed)

static size_t s_seed = 940983058;

void setSeed(int seed) { s_seed = seed; }

size_t rng()
{
    size_t x = s_seed;
    x ^= x << 17;
    x ^= x >> 19;
    x ^= x << 13;
    s_seed = x;
    return x;
}

size_t rng(size_t min, size_t max)
{
    if(min >= max) return std::string::npos;
    if(min == max) return min;

    size_t x = s_seed;
    x ^= x << 17;
    x ^= x >> 19;
    x ^= x << 13;
    s_seed = x;
    
    // apply the limits
    x = (x % (max - min)) + min;
    return x;
}