advent_of_code_2025/4/solve_1.go

package main

import (
	"bufio"
	"fmt"
	"os"
)

type coord struct {
	x,y,nb_neighbors int
	
}

func update_neighbors(positions* []*coord, i,j int) int{
	nbn := 0
	for _, paper_roll := range *positions {
		switch(paper_roll.x){
			case i:
			switch(paper_roll.y){
				case j-1, j+1:
				nbn++
				paper_roll.nb_neighbors++
			}
			case i-1, i+1:
			switch(paper_roll.y){
				case j-1,j,j+1:
				nbn++
				paper_roll.nb_neighbors++
			}
		}
	}
	return nbn
}

func main() {
	fmt.Println("Advent of Code 2025 - Day 4 - Part 1")
	f,_ := os.Open("4/input")
	defer f.Close()

	var positions []*coord
	scanner := bufio.NewScanner(f)
	line_num := 0
	res := 0
	for scanner.Scan() {
		line := scanner.Text()
		for i:= 0; i < len(line); i++{
			if line[i] == '@'{
				nbn := update_neighbors(&positions,line_num,i)
				positions = append(positions, &coord{line_num,i,nbn})
			}
		}
		line_num++
	}

	for _, paper_roll := range positions {
		if paper_roll.nb_neighbors < 4 {res ++}
	}
	
	fmt.Println(res)
}