rand-取小于一个定值M以内，N个不重复的数（M>=N）
//rand.c#include "rand.h"int * randToArray(int array[], int len, int value){int i;int random,tmp;for(i = 0; i < value; i++)array[i] = i + 1;srand(time(NULL));for(i = 0; i < len; i++){random = rand()%(value-i)+i;//最小值在变，random即是随机数又是数组下标tmp = array[i];array[i] = array[random];array[random] = tmp;}return array;}int main(void){int array[20],i;int *p = array;p = randToArray(array,20,20);//不能是arrayprintf("the random array:\n");for(i = 0; i < 20; i++){printf("%d ",*(p+i));}printf("\n");return 0;}