advent_of_code_2025/8/solve_2.go

package main

import (
	"bufio"
	"fmt"
	"math"
	"os"
	"slices"
	"sort"
	"strconv"
	"strings"
)

func main(){
	fmt.Println("Advent of Code 2025 - Day 8 - Part 1")
	f,_:=os.Open("8/input")
	defer f.Close()

	var junction_boxes [][]int64
	
	scanner := bufio.NewScanner(f)
	for scanner.Scan(){
		line := scanner.Text()
		var coords []int64
		for c := range strings.SplitSeq(line, ","){
			c_i,_ := strconv.ParseInt(c,10,64)
			coords = append(coords, c_i)
		}
		junction_boxes = append(junction_boxes, coords)
	}
	distances := calculate_distances(junction_boxes)
	b1,b2 := create_circuits(distances, len(junction_boxes))
	res := junction_boxes[b1][0] * junction_boxes[b2][0]
	fmt.Println(res)
}

func create_circuits(distances sj_box_distances, nb_jb int) (int,int) {
	res1,res2 := 0,0
	var circuits [][]int
	circuits = append(circuits, []int{distances[0].b1, distances[0].b2})
	for i := 1; i < len(distances); i++ {
		b1,b2 := distances[i].b1, distances[i].b2
		new := true
		for cir := range circuits {
			ok1, ok2 := slices.Contains(circuits[cir],b1), slices.Contains(circuits[cir],b2)
			if ok1 && ok2 {
				new = false
				break
			} else if ok1 && !ok2 {
				new = false
				merge_circuits(cir, b2, &circuits)
				break
			} else if !ok1 && ok2 {
				new = false
				merge_circuits(cir, b1, &circuits)
				break
			}
		}
		if new {
			circuits = append(circuits, []int{b1,b2})
		}
		if len(circuits) == 1 && len(circuits[0]) == nb_jb {
			res1,res2 = b1,b2
			break
		}
	}
	
	return res1,res2
}

func merge_circuits(idx_cir, box int, circuits* [][]int) {
	idx_cir_tomerge := -1
	for i := range *circuits{
		if slices.Contains((*circuits)[i],box){
			idx_cir_tomerge = i
		}
	}
	if idx_cir_tomerge >= 0 {
		(*circuits)[idx_cir] = append((*circuits)[idx_cir], (*circuits)[idx_cir_tomerge]...)
		(*circuits)[idx_cir_tomerge] = (*circuits)[len(*circuits)-1]
		(*circuits) = (*circuits)[:len(*circuits)-1]
	} else {
		(*circuits)[idx_cir] = append((*circuits)[idx_cir], box)
	}
}

type j_box_distance struct {
	b1,b2 int
	dis float64
}

type sj_box_distances []j_box_distance

func (a sj_box_distances) Len() int { return len(a)}
func (a sj_box_distances) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
func (a sj_box_distances) Less(i, j int) bool { return a[i].dis < a[j].dis }


func calculate_distances(points [][]int64) sj_box_distances {
	var res sj_box_distances
	for i := range(points) {
		for j := i+1; j < len(points); j++{
			b1,b2 := i,j
			dis := euclidiean_distance(points[i],points[j]) 
			res = append(res, j_box_distance{b1,b2,dis})
		}
	}
	sort.Sort(res)
	return res
}

func euclidiean_distance(p1, p2 []int64) float64 {	
	dx,dy,dz := math.Pow(float64(p1[0] - p2[0]), 2.0), math.Pow(float64(p1[1] - p2[1]), 2.0), math.Pow(float64(p1[2] - p2[2]), 2.0)
	return math.Sqrt(dx + dy + dz)
}