代码：
#include <stdio.h>
#include <time.h>
int main(void){
     char v[]=("1 2 3 4 5 6 7 8 9 0");
     unsigned seed=time(NULL);
     srand(seed);
     printf("%c",v[rand()%10]);
}

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main(void){
     char v[]="1234567890";
     unsigned seed=time(NULL);
     srand(seed);
     printf("%c",v[rand()%10]);
}

srand函數包含在stdlib.h庫中
你忘了include stdlib.h了

谢谢各位