Warning: session_start(): open(/tmp/sess_e11eb6d61875af7d11b9ec860954824f, O_RDWR) failed: No space left on device (28) in /data/wiki/inc/init.php on line 239

Warning: session_start(): Failed to read session data: files (path: ) in /data/wiki/inc/init.php on line 239

Warning: Cannot modify header information - headers already sent by (output started at /data/wiki/inc/init.php:239) in /data/wiki/inc/auth.php on line 430

Warning: mkdir(): No space left on device in /data/wiki/lib/plugins/dw2pdf/vendor/mpdf/mpdf/src/Cache.php on line 19
Temporary files directory "/data/wiki/data/tmp/dwpdf/266/" is not writable

Warning: Cannot modify header information - headers already sent by (output started at /data/wiki/inc/init.php:239) in /data/wiki/inc/actions.php on line 38

Warning: Cannot modify header information - headers already sent by (output started at /data/wiki/inc/init.php:239) in /data/wiki/lib/tpl/dokuwiki/main.php on line 12
2020-2021:teams:manespace:codeforces_round_646_div2 [CVBB ACM Team]

用户工具

站点工具


2020-2021:teams:manespace:codeforces_round_646_div2

codeforces round 646(div2)

A

谁说签到都是水题的?

题意:从$n$个数中选择$x$个数,要求选出来的数满足,这$x$个数的和为奇数,问给的这一系列数能不能满足这个条件。

题解:首先有一个比较基本的结论,只有奇数个奇数相加才会出现奇数,否则出现的一定是偶数。所以先统计这个$n$个数中有多少奇数,比较奇数的数量与$x$的大小,如果$x$的值小,则判断$x$是否为偶数,若是偶数,判断原序列是否有偶数存在,若无则一定不成立。如果$x$的值大,则判断奇数个数的奇偶性,若为奇数,一定成立,若为偶数,则判断是否存在偶数,不存在一定不存在。这坑太多了

B

题意:

2020-2021/teams/manespace/codeforces_round_646_div2.1591521020.txt.gz · 最后更改: 2020/06/07 17:10 由 iuiou