sheet 1 - upsolve part 1

sheet link : vjudge.net/gro...
All codes : github.com/ICP...
Timeline:
0:00:34 problem A
0:03:34 problem B
0:11:08 problem C
0:15:27 problem D
0:19:00 problem E
0:25:03 problem F
0:39:36 problem G
0:51:13 problem H
0:59:15 problem I
1:05:30 problem J
1:21:44 problem K
1:33:41 problem L
1:43:10 problem M