AoC23/d05.go

package main

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

type maprange struct {
    src uint64
    dst uint64
} 

type mapdir struct {
	src string
	dst string
}

type mapval struct {
    cunt uint64
    rnge maprange
}

type mapping struct {
    dir mapdir
    val []mapval
}

func parse(f *os.File) (seeds []uint64, maps []mapping) {
    s := bufio.NewScanner(f)

    inmap := false
    var curmap mapping
    for s.Scan() {
        line := s.Text()
        switch {
        case strings.HasPrefix(line, "seeds: "):
            thing := strings.Split(line[7:], " ")
            for _, v := range thing {
                val, _ := strconv.ParseUint(v, 0, 64)
                seeds = append(seeds, val)
            }

        case strings.HasSuffix(line, " map:"):
            if inmap { maps = append(maps, curmap) }
            curmap = mapping{}
            inmap = true

            split1 := strings.Index(line, "-to-")
            split2 := strings.Index(line, " ")
            src := line[:split1]
            dst := line[split1 + 4:split2]
            curmap.dir.src = src
            curmap.dir.dst = dst

        case strings.Count(line, " ") >= 2 && inmap:
            thing := strings.Split(line, " ")
            var val mapval
            val.rnge.dst, _ = strconv.ParseUint(thing[0], 0, 64)
            val.rnge.src, _ = strconv.ParseUint(thing[1], 0, 64)
            val.cunt, _ = strconv.ParseUint(thing[2], 0, 64)
            curmap.val = append(curmap.val, val)
        }
    }
    if inmap { maps = append(maps, curmap) }

    return
}

func part1(init_seeds []uint64, maps []mapping) uint64 {
    seeds := append(make([]uint64, 0, len(init_seeds)), init_seeds...)

    currency := "seed"
    for currency != "location" {
        var map_cur mapping
        map_found := false
        for _, v := range maps {
            if v.dir.src == currency {
                map_cur = v
                map_found = true
                break
            }
        }
        if !map_found { break }

        currency = map_cur.dir.dst
        for i, v := range seeds {
            for _, x := range map_cur.val {
                tmp := v - x.rnge.src
                if tmp > 0 && tmp < x.cunt {
                    v += x.rnge.dst - x.rnge.src
                    break
                }
            }
            seeds[i] = v
        }
    }

    min := seeds[0]
    for _, v := range seeds[1:] {
        if v < min { min = v }
    }
    return min
}

func part2(init_seeds []uint64, maps []mapping) uint64 {
    seeds := make([]maprange, 0)
    for i, _ := range init_seeds {
        if i % 2 == 1 { continue }
        var rnge maprange
        rnge.src = init_seeds[i + 0]
        rnge.dst = rnge.src + init_seeds[i + 1]
        seeds = append(seeds, rnge)
    }

    currency := "seed"
    for currency != "location" {
        var map_cur mapping
        map_found := false
        for _, v := range maps {
            if v.dir.src == currency {
                map_cur = v
                map_found = true
                break
            }
        }
        if !map_found { break }

        currency = map_cur.dir.dst
        newseedrnge := make([]maprange, 0)
        for _, v := range seeds {
            for _, x := range map_cur.val {
                src := x.rnge.src
                end := x.rnge.src + x.cunt
                if src <= v.src && v.src < end && src <= v.dst && v.dst < end {
                    newseedrnge = append(newseedrnge, maprange{
                        src: v.src + x.rnge.dst - x.rnge.src,
                        dst: v.dst + x.rnge.dst - x.rnge.src,
                    })
                    v.src = v.dst
                } else if src <= v.src && v.src < end {
                    newseedrnge = append(newseedrnge, maprange{
                        src: v.src + x.rnge.dst - x.rnge.src,
                        dst: x.rnge.dst + x.cunt,
                    })
                    v.src = end
                } else if src <= v.dst && v.dst < end {
                    newseedrnge = append(newseedrnge, maprange{
                        src: x.rnge.dst,
                        dst: v.dst + x.rnge.dst - x.rnge.src,
                    })
                    v.dst = src
                }
                if v.src == v.dst { break }
            }
            if v.src != v.dst { newseedrnge = append(newseedrnge, v) }
        }
        seeds = newseedrnge
    }

    minrnge := seeds[0].src
    for _, v := range seeds[1:] {
        if v.src < minrnge { minrnge = v.src }
    }
    return minrnge
}

func main() {
	f, _ := os.Open(os.Args[1])

    seeds, maps := parse(f)
    fmt.Println(part1(seeds, maps))
    fmt.Println(part2(seeds, maps))
}