C语言随机数函数

/* rand0.c –– produces random numbers            */
/*               uses ANSI C portable algorithm  */
static unsigned long int next = 1;  /* the seed  */

unsigned int rand0(void)
{
    /* magic formula to generate pseudorandom number */
    next = next * 1103515245 + 12345;
    return (unsigned int) (next/65536) % 32768;
}

/* r_drive0.c -- test the rand0() function */
/* compile with rand0.c                    */
#include <stdio.h>
extern unsigned int rand0(void);

int main(void)
{
    int count;

    for (count = 0; count < 5; count++)
        printf("%d\n", rand0());

    return 0;
}

/* s_and_r.c -- file for rand1() and srand1()    */
/*                uses ANSI C portable algorithm */
static unsigned long int next = 1;  /* the seed  */

int rand1(void)
{
    /* magic formula to generate pseudorandom number */
    next = next * 1103515245 + 12345;
    return (unsigned int) (next/65536) % 32768;
}

void srand1(unsigned int seed)
{
    next = seed;
}

/* r_drive1.c -- test rand1() and srand1() */
/* compile with s_and_r.c                  */
#include <stdio.h>
#include <stdlib.h>
extern void srand1(unsigned int x);
extern int rand1(void);

int main(void)
{
    int count;
    unsigned seed;

    printf("Please enter your choice for seed.\n");
    while (scanf("%u", &seed) == 1)
    {
        srand1(seed);    /* reset seed */
        for (count = 0; count < 5; count++)
            printf("%d\n", rand1());
        printf("Please enter next seed (q to quit):\n");
    }
    printf("Done\n");

    return 0;
}