Keep track of the current maximum, as well as the current Elf's sum as you go through the list. Everytime you see a newline, reset the current sum.
Similar to part 1, but store the sums in an array everytime you see a newline. Sort the resulting array and take the 3 largest elements.
Leaderboard filled up pretty quickly, missed top 100 by 10-20 seconds for both parts.