advent_of_code_2025/6/solve_2.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)


func main(){
	fmt.Println("Advent of Code 2025 - Day 6 - Part 2")
	f,_:=os.Open("6/input")
	defer f.Close()
	scanner:=bufio.NewScanner(f)
	var input []string
	var grid [][]string
	for scanner.Scan(){
		line:= scanner.Text()
		input = append(input, line)
	}
	
	grid = define_columns(input)
	operators := extract_operators(input[len(input)-1])
	
	n := len(grid)
	m := len(grid[0])

	// Calculate the transpose
	transpose_operands_matrix := make([][]string, m)
	for j:= range m{
		transpose_operands_matrix[j] = make([]string, n)
		for i:= range n{
			transpose_operands_matrix[j][i] = grid[i][j]
		}
	}

	// Calculate with the new digit disposition
	new_operands_matrix := make([][]string, m)
	for j:= range m{
		new_operands_matrix[j] = make([]string,n)
		for range n{
			new_operands_matrix[j] = align_digits(transpose_operands_matrix[j])
		}
	}

	res := int64(0)
	for i,operation:= range new_operands_matrix {
		operator := operators[i]
		res += calculate(operator, operation)
	}
	fmt.Println(res)
}

func define_columns(input []string) [][]string{
	var res [][]string
	operands := input[len(input)-1]
	var columns_widths []int
	col_width := 0
	first := true
	for i := range operands {
		if operands[i] != ' '{
			if (first){
				first = false
			} else {
				columns_widths = append(columns_widths, col_width)
				col_width = 0
			}
		} else {
			col_width++
		}
		if (i==len(operands)-1){
			columns_widths = append(columns_widths, col_width+1)
		}
	}
	for _,line := range input[:len(input)-1] {
		operation := split_line(line, columns_widths)
		res = append(res, operation)
	}	
	return res
}

func split_line(line string, column_widths []int) []string{
	var res []string
	offset := 0
	for _,w := range column_widths {
			res = append(res, line[offset:offset+w])
			offset += w+1
	}
	return res
}

func align_digits(operands []string) []string {
	var res []string
	n := len(operands[0])
	for i:=range n {
		nop := ""
		for _,op := range operands{
			nop += string(op[i])
		}
		res = append(res, nop)
	}
	return res
}

func extract_operators(ops string) []string{
	var res []string
	for op := range strings.SplitSeq(ops," ") {
		if (len(op) > 0){
			res = append(res, op)
		}
	}
	return res
}

func calculate(operator string, operands []string) int64{
	var res int64
	switch(operator){
		case "*":
		res = int64(1)
		for _,op := range operands{
			op = strings.TrimSpace(op)
			op_toi,_ := strconv.ParseInt(op,10,64)
			res *= op_toi
		}
		case "+":
		res = int64(0)
		for _,op := range operands{
			op = strings.TrimSpace(op)
			op_toi,_ := strconv.ParseInt(op,10,64) 
			res += op_toi
		}
	}
	return res
}