add day5

day5/day5.go

@@ -0,0 +1,143 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+)
+
+const MaxInt = int((^uint(0) >> 1))
+
+type Range struct {
+	dst int
+	src int
+	len int
+}
+
+func (r Range) Map(n int) (int, bool) {
+	if n < r.src || n > (r.src+r.len-1) {
+		return 0, false
+	}
+	return r.dst - r.src + n, true
+}
+
+type Map struct {
+	name   string
+	ranges []Range
+}
+
+func (m *Map) Append(r Range) {
+	m.ranges = append(m.ranges, r)
+}
+
+func (m *Map) Map(n int) int {
+	for i := range m.ranges {
+		x, ok := m.ranges[i].Map(n)
+		if ok {
+			return x
+		}
+	}
+	return n
+}
+
+type Almanac struct {
+	seeds []int
+	maps  []*Map
+}
+
+func (a *Almanac) ParseFile(name string) error {
+	f, err := os.Open(name)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	scanner := bufio.NewScanner(f)
+	scanner.Scan()
+	seedsStr := scanner.Text()
+	seeds := strToInts(seedsStr[7:])
+	a.seeds = seeds
+	scanner.Scan()
+	var m *Map
+	for scanner.Scan() {
+		s := scanner.Text()
+		s = strings.Trim(s, " \n")
+		if s == "" {
+			a.maps = append(a.maps, m)
+			continue
+		}
+		if s[0] > '9' {
+			m = &Map{
+				name:   s,
+				ranges: []Range{},
+			}
+			continue
+		}
+		nums := strToInts(s)
+		r := Range{
+			dst: nums[0],
+			src: nums[1],
+			len: nums[2],
+		}
+		m.Append(r)
+	}
+	a.maps = append(a.maps, m)
+	return nil
+}
+
+func (a *Almanac) seedToLoc(n int) int {
+	for i := range a.maps {
+		n = a.maps[i].Map(n)
+	}
+	return n
+}
+
+func (a *Almanac) ClosestForSeeds() int {
+	result := MaxInt
+	for _, n := range a.seeds {
+		loc := a.seedToLoc(n)
+		if loc < result {
+			result = loc
+		}
+	}
+	return result
+}
+
+func (a *Almanac) ClosestForRanges() int {
+	result := MaxInt
+	for i := 0; i < (len(a.seeds) - 2); i += 2 {
+		for j := a.seeds[i]; j < (a.seeds[i] + a.seeds[i+1]); j++ {
+			loc := a.seedToLoc(j)
+			if loc < result {
+				result = loc
+			}
+		}
+	}
+	return result
+}
+
+func strToInts(s string) []int {
+	s = strings.Trim(s, " \n")
+	split := strings.Split(s, " ")
+	nums := []int{}
+	for _, x := range split {
+		n, err := strconv.Atoi(x)
+		if err != nil {
+			panic(err)
+		}
+		nums = append(nums, n)
+	}
+	return nums
+}
+
+func main() {
+	a := new(Almanac)
+	a.ParseFile("input.txt")
+
+	x := a.ClosestForSeeds()
+	fmt.Println(x)
+
+	y := a.ClosestForRanges()
+	fmt.Println(y)
+}