生成不重复随机数

       Random random = new Random();
int[] mat = new int[num];
int i, p=0, tmp=0;
for(i=0;i<num;i++)
mat[i] = i;
for (i = num-1; i >= 0;i-- )
{
p = random.Next(0, i);
tmp = mat[p];
mat[p] = mat[i];
mat[i] = tmp;
}