advent_of_code_2025/5/solve_2.go

package main

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

type interval struct {
	lb,ub int64
}

type sinterval []interval

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

func main(){
	fmt.Println("Advent of Code 2025 - Day 5 - Part 2")
	f,_:= os.Open("5/input")
	defer f.Close()
	scanner := bufio.NewScanner(f)

	var ranges []interval;
	
	for scanner.Scan(){
		line := scanner.Text()
		if (len(line) == 0){
			break
		}
		line_split := strings.Split(line, "-")
		lb,_ := strconv.ParseInt(line_split[0],10,64)
		ub,_ := strconv.ParseInt(line_split[1],10,64)
		ranges = append(ranges, interval{lb,ub})
	}

	res := int64(0)
	sort.Sort(sinterval(ranges))

	var compressed_ranges []interval;
	for _, itvl := range ranges{
		if (len(compressed_ranges)==0){
			compressed_ranges = append(compressed_ranges, itvl)
		} else {
			last_compressed := &compressed_ranges[len(compressed_ranges)-1]
			if (last_compressed.ub >= itvl.lb){
				last_compressed.ub = max(itvl.ub, last_compressed.ub)
			} else {
				compressed_ranges = append(compressed_ranges, itvl)				
			}
		}
	}

	for _,itvl := range compressed_ranges{
		res += itvl.ub - itvl.lb + 1
	}
	
	fmt.Println(res)
}