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？ 1.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。 -A host of companies are looking to shake-up the ways we interact with computers. Using new motion sensing technology they aim for users to replace typing and mouse-clicking with some of the gestures and movements used in everyday life. WSJ s Jessica Vascellaro reports.