有1、2、3、4个数字，能组成多少个互不相同且无重复数字的三位数？都是多少？

程序分析：可填在百位、十位、个位的数字都是1、2、3、4。组成所有的排列后再去

　　　　　　掉不满足条件的排列。

-With 1,2,3,4 numbers, how many can be composed with each other and not repeat the three-digit numbers? Are how much? Program analysis: can fill in one hundred, ten, one-bit numbers are 1,2,3,4. Then remove all of the order form does not meet the conditions of the arrangement.