c语言随机数

 

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main()
{
        srand((unsigned)time(NULL));    //初始化随机数
        /*random int number [0,a), e.g.[0,10)*/
        int a1=rand()%10;
        /*random int number [a,b), e.g.[10,20)*/
        int a2=(rand()%(20-10))+10;
        /*random float number 0~1*/
        double a3=rand()/(double)(RAND_MAX);
        /*random float number 0~n, e.g.0~100*/
        double a4=rand()/((double)(RAND_MAX)/100);

        printf("a1=%d\n",a1);
        printf("a2=%d\n",a2);
        printf("a3=%f\n",a3);
        printf("a4=%f\n",a4);
        return 0;

}