Python-实列

 """题目：有四个数字：1、2、3、4，能组成多少个互不相同且无重复数字的三位数？各是多少？
 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。"""
 # 三种实现方法

 for i in range(1, 433):
     i = str(i)
     if len(i) == 3:
         if i[1] not in ['', '', '', '', '', ''] and i[2] not in ['', '', '', '', '', '']:
             if i[0] not in i[1] and i[0] not in i[2] and i[1] not in i[2]:
                 print(i)

 for a in range(1, 5):
     for b in range(1, 5):
         for c in range(1, 5):
             if a != b and a != c and b != c:
                 print(a, b, c)

 list_num = [1, 2, 3, 4]
 for i in list_num:
     for j in list_num:
         for k in list_num:
             if j != i and k != j and k != i:
                 print(i*100+j*10+k)