aoc2025/day05/Notes.md

Day 5: Notes

Star 1

• for each ID, for each interval, check if ID is in interval
• could be parallelized
  • goroutine for each ID - sounds okay
  • also goroutines for intervals - overkill?

Interval:

type Interval struct {
	From int
	To   int
}

func (i *Interval) In(val int) bool {
	return i.From <= val && val <= i.To
}

Star 2

• intervals need to be merged
• to do that efficiently, they need to be sorted
• then, a sequence of intervals can be merged:

100596811663215  -  100867276610455
100596811663215  -  101195447377813
100596811663215  -  101195447397536

100596811663215  -  101195447397536

• start of first and end of last
• iterate over list of intervals
• find furthest matching start
• copy new merged interval into separate list

Attempts

• 323939472567605: too low
• 422408896659291: too high