We started about 50 mins after the contest had begun.
#I AC 61 mins
Brute force
#E AC 105 mins
Greedy
#A AC 113 mins 2 wrong tries by WHD
#C AC 126 mins 1 wrong try
AC automation
#H AC 153 mins 1 wrong try
Math
#F AC 224 mins 1 wrong try
Game theory
#B AC 259 mins 5 wrong tries
The solution for this problem is first written by WHD. I rewrote it and got AC after 1 wrong try.
#J AC 284 mins 4 wrong tries by WHD
WHD used a right algorithm to solve this problem, but made a small mistake. After I found it out, WHD corrected it and got AC.