排列组合在一本４００页的书中，数
1~100出现过:1,10,11,12,13,14,15,16,17,18,19,21,31,41,51,61,71,81,91,100共21个
101~200出现过:除200外的所有数字,出现两~三次的有:101,110,111,112,113,114,115,116,117,118,119,121,131,141,151,161,171,181,191
总共有119个
201~300出现过:201,210,211,212,213,214,215,216,217,218,219,221,231,241,251,261,271,281,291共20个
301~400共出现过:301,310...全部
1~100出现过:1,10,11,12,13,14,15,16,17,18,19,21,31,41,51,61,71,81,91,100共21个
101~200出现过:除200外的所有数字,出现两~三次的有:101,110,111,112,113,114,115,116,117,118,119,121,131,141,151,161,171,181,191
总共有119个
201~300出现过:201,210,211,212,213,214,215,216,217,218,219,221,231,241,251,261,271,281,291共20个
301~400共出现过:301,310,311,312,313,314,315,316,317,318,319,321,331,341,351,361,371,381,391共20个
所以,1~400共出现了180个1
从我出生到现在还没看到过从1到1亿的题啊
如果有的话,就一定要分类讨论了,这类题没有固定算式。
收起
