#+title: Notes
* part 2 and i'm struggling.
maybe i need to mark 'inside' cells while i dig?
i don't know which is 'outside' from the getgo?

if i mark 'all the rightside', will that help to calculate inside?
* well, if we dont' have instruction with steps:1 i can just count points above and belove the line
without more complicated things

just count 'seenUp' and 'seenDown' if equal - then we changed side

and - we shouldn't have 'step1' because all numbers are soooo big.

ok. let's do that? with maps of cols.
** CANCELLED add map[row]map[col]any
** CANCELLED separate method to set it up after we have all of the BorderCellCols
** CANCELLED during digInsides on each consecutive - check above and below and count
when there's a jump - compare counts, to make decision on whether to switch 'isInside'
** no. just because they are long doesn't mean they won't ever get one near another
* another idea is to save | and corners, as if we're going from left to right
this seems reasonable.
** DONE i guess []SpecialSymbol which has Col and Symbol
** DONE no, let's make it map. yes will have to init, but yuck anyway
** TODO then different logic on border building.
if U \ D - on all but last add '|'
on last - calc with the next turn, what should be saved 'as if traversing from the left'

for L \ R - on last - calc what the turn was
** TODO !! between last and first movement the corner is unknown.
so, copy the first instruction to the end?
** moment of hope.
my calculation for example input for part 2
day18 result: 952408144115

952408144115
*** YES.
*** about 1M for 4 minutes
** so, my input is ~16M rows
3.5 seconds per 10k
** well, maybe i can parallel.
*** parallel example
day18 result: 952407566854
*** and with separate done channel from the summing goroutine
952408144115
**** YES