摘要: 习题 阅读全文
posted @ 2019-04-05 16:19 LXL_1 阅读(390) 评论(0) 推荐(0) 编辑
摘要: # Topic: There are four digits: 1, 2, 3 and 4. # How many different three digits can be formed without repeating numbers? How much is each? # Procedure analysis: traverse all possibilities and shav... 阅读全文
posted @ 2019-04-05 14:14 LXL_1 阅读(277) 评论(0) 推荐(0) 编辑