last 3 days

24/24.go

@@ -0,0 +1,113 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+)
+
+// cat input | go run 24.go
+
+type comp struct {
+	a int
+	b int
+}
+
+type bridge struct {
+	components []comp
+	last       int
+}
+
+func main() {
+
+	scanner := bufio.NewScanner(os.Stdin)
+	var components = []comp{}
+
+	for scanner.Scan() {
+		s := strings.Split(scanner.Text(), "/")
+		a, _ := strconv.Atoi(s[0])
+		b, _ := strconv.Atoi(s[1])
+		c := comp{a, b}
+		components = append(components, c)
+	}
+
+	b := bridge{[]comp{}, 0}
+	bridges := []bridge{b}
+	oldcount := -1
+
+	for oldcount != 0 {
+		nb := []bridge{}
+		oldcount = 0
+		for x := range bridges {
+			c, tb := BuildBridges(bridges[x], components)
+			oldcount += c
+			nb = append(nb, tb...)
+		}
+		bridges = nb
+	}
+
+	maxlen := 0
+	for p := range bridges {
+		if len(bridges[p].components) > maxlen {
+			maxlen = len(bridges[p].components)
+		}
+	}
+
+	maxtot := 0
+	maxlongest := 0
+	for p := range bridges {
+		tot := 0
+		for x := range bridges[p].components {
+			tot += bridges[p].components[x].a
+			tot += bridges[p].components[x].b
+		}
+		if len(bridges[p].components) == maxlen && tot > maxlongest {
+			maxlongest = tot
+		}
+		if tot > maxtot {
+			maxtot = tot
+		}
+	}
+	fmt.Println(maxtot, maxlongest)
+
+}
+
+func BuildBridges(b bridge, components []comp) (int, []bridge) {
+	var bridges = []bridge{}
+
+	used := 0
+	for c := range components {
+
+		tc := components[c]
+		if isUsable(tc, b.components) && (tc.a == b.last || tc.b == b.last) {
+			used++
+			nb := make([]comp, len(b.components))
+			copy(nb, b.components)
+			nb = append(nb, tc)
+			nlast := -1
+			if tc.a == b.last {
+				nlast = tc.b
+			} else {
+				nlast = tc.a
+			}
+			newbridge := bridge{nb, nlast}
+			bridges = append(bridges, newbridge)
+		}
+	}
+	if used == 0 {
+		bridges = append(bridges, b)
+	}
+
+	return used, bridges
+}
+
+func isUsable(n comp, h []comp) bool {
+	for c := range h {
+		if n.a == h[c].a && n.b == h[c].b {
+			return false
+		}
+	}
+	return true
+}