evan.jarrett.net
no this isn't about alexandria ocasio-cortez
1package main
2
3import (
4 "fmt"
5 "slices"
6 "strconv"
7 "strings"
8
9 "tangled.org/evan.jarrett.net/aoc2025/internal/puzzle"
10)
11
12type IDRange struct {
13 first int
14 last int
15}
16
17type DayFive struct {
18 freshIds []IDRange
19 tocheck []int
20}
21
22func (d *DayFive) ParseInput(input string) error {
23 for line := range strings.SplitSeq(strings.TrimSpace(input), "\n") {
24 line = strings.TrimSpace(line)
25 if strings.Contains(line, "-") {
26 splits := strings.Split(line, "-")
27 first, _ := strconv.Atoi(splits[0])
28 last, _ := strconv.Atoi(splits[1])
29 d.freshIds = append(d.freshIds, IDRange{first, last})
30 } else if line == "" {
31 continue
32 } else {
33 ingredient, _ := strconv.Atoi(line)
34 d.tocheck = append(d.tocheck, ingredient)
35 }
36 }
37 return nil
38}
39
40func (d *DayFive) Part1() (int, error) {
41 count := 0
42 for _, i := range d.tocheck {
43 for _, idrange := range d.freshIds {
44 if i >= idrange.first && i <= idrange.last {
45 count++
46 break
47 }
48 }
49 }
50 return count, nil
51}
52
53func (d *DayFive) Part2() (int, error) {
54 count := 0
55
56 slices.SortFunc(d.freshIds, func(a, b IDRange) int {
57 return a.first - b.first
58 })
59 var combinedFreshIds []IDRange
60 last := d.freshIds[0]
61 for _, current := range d.freshIds {
62 if current.first <= last.last {
63 last.last = max(last.last, current.last)
64 } else {
65 combinedFreshIds = append(combinedFreshIds, last)
66 last = current
67 }
68 }
69 // combine one last time
70 combinedFreshIds = append(combinedFreshIds, last)
71
72 for _, idrange := range combinedFreshIds {
73 numInRange := idrange.last - idrange.first + 1
74 fmt.Println(numInRange)
75 count += numInRange
76 }
77 return count, nil
78}
79
80func main() {
81 puzzle.Run(5, &DayFive{})
82}