在 C 中播种 rand() 并指定值

Question

If you wanted a random number generator to use ints 2,5,7,4 and you seed your generator with

srand(2,5,7,4)

printf("%d \n",rand())

Is this flawed in accomplishing that?

Answer 1

That is not how it works. An PRNG uses an algorithm to generate a sequence of numbers with random like behaviour. For a given seed, a given sequence of numbers will be generated, what those number are is entirely up to the algorithm used.

to get a random number for a list, you will need something like:

n = list[rand() % (sizeof(list) / sizeof(list[0])];

Answer 2

In case you want to print a value from a given array randomly on each execution, you may consider using the following:

#include<stdio.h>
#include<time.h>
#include<stdlib.h>

int main() {
    srand ( time(NULL) ); // accepts one argument only

    int myArray[4] = { 2,5,7,4 }; // array required
    int randomIndex = rand() % 4; // limiting randomness
    int randomValue = myArray[randomIndex]; // choosing one of the random numbers

    printf("Random value from array: %d\n", randomValue); // simply prints
    return 0;
}