2017 day 12 done!

2017/day12/day12.go

@@ -0,0 +1,128 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+)
+
+var progs map[int][]int
+var groups map[int][]int
+
+func main() {
+	inp := StdinToStrings()
+	part1(inp)
+	part2()
+}
+
+func part1(inp []string) {
+	progs = make(map[int][]int)
+	for i := range inp {
+		pts := strings.Split(inp[i], " ")
+		mn := Atoi(pts[0])
+
+		for _, v := range pts[2:] {
+			if v[len(v)-1] == ',' {
+				v = v[:len(v)-1]
+			}
+			if v = strings.TrimSpace(v); v != "" {
+				sub := Atoi(v)
+				progs[mn] = append(progs[mn], sub)
+			}
+		}
+	}
+	var res int
+	for k := range progs {
+		if pRes, _ := progCanAccess(k, 0, []int{}); pRes {
+			res++
+		}
+	}
+	fmt.Println(res, "programs can access zero")
+}
+
+func part2() {
+	groups = make(map[int][]int)
+	for k, v := range progs {
+		isNew := true
+		for gk := range groups {
+			if can, _ := progCanAccess(k, gk, []int{}); can {
+				AddToGroup(gk, k)
+				isNew = false
+				break
+			}
+		}
+		if isNew {
+			// We went through all groups and couldn't access any
+			groups[k] = v
+		}
+	}
+	fmt.Println(len(groups), "total groups")
+}
+
+func AddToGroup(grp, prog int) {
+	if !SliceContains(groups[grp], prog) {
+		groups[grp] = append(groups[grp], prog)
+	}
+	for _, v := range progs[prog] {
+		if !SliceContains(groups[grp], v) {
+			groups[grp] = append(groups[grp], v)
+		}
+	}
+}
+
+func progCanAccess(st, end int, tried []int) (bool, []int) {
+	// Have we already tried this one?
+	if SliceContains(tried, st) {
+		return false, tried
+	}
+	tried = append(tried, st)
+
+	// Is this it?
+	if st == end {
+		return true, tried
+	}
+
+	// Is it direct?
+	if SliceContains(progs[st], end) {
+		return true, tried
+	}
+
+	// Ok, recurse
+	var res bool
+	for _, v := range progs[st] {
+		if res, tried = progCanAccess(v, end, tried); res {
+			return res, tried
+		}
+	}
+	return false, tried
+}
+
+func SliceContains(sl []int, tgt int) bool {
+	for i := range sl {
+		if sl[i] == tgt {
+			return true
+		}
+	}
+	return false
+}
+
+func StdinToStrings() []string {
+	var input []string
+	scanner := bufio.NewScanner(os.Stdin)
+	for scanner.Scan() {
+		input = append(input, scanner.Text())
+	}
+	return input
+}
+
+func Atoi(i string) int {
+	var ret int
+	var err error
+	if ret, err = strconv.Atoi(i); err != nil {
+		log.Fatal("Invalid Atoi")
+	}
+	return ret
+}