adventofcode/2017/day24/day24.go

package main

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

var comps []Component
var strongest, best Bridge

func main() {
	inp := StdinToStrings()
	for i := range inp {
		comps = append(comps, NewComponent(inp[i]))
	}

	FindStrongest([]Component{NewComponent("0/0")})
	fmt.Println("Strongest:\n", strongest)

	FindBest([]Component{NewComponent("0/0")})
	fmt.Println("Best:\n", best)
}

// Strongest, regardless of length
func FindStrongest(bridge Bridge) {
	if bridge.Strength() > strongest.Strength() {
		strongest = bridge
	}
	for i := range comps {
		if comps[i].Has(bridge.Needs()) && !bridge.Has(comps[i]) {
			FindStrongest(append(bridge, comps[i]))
		}
	}
}

// Longest and Strongest
func FindBest(bridge Bridge) {
	if bridge.Length() > best.Length() {
		best = append([]Component{}, bridge...)
	} else if bridge.Length() == best.Length() {
		if bridge.Strength() > best.Strength() {
			best = bridge
		}
	}

	for i := range comps {
		if comps[i].Has(bridge.Needs()) && !bridge.Has(comps[i]) {
			FindBest(append(bridge, comps[i]))
		}
	}
}

type Bridge []Component

func (b Bridge) Strength() int {
	var ret int
	for _, v := range []Component(b) {
		ret += v.Strength()
	}
	return ret
}

func (b Bridge) Has(c Component) bool {
	for _, v := range []Component(b) {
		if v.Name == c.Name {
			return true
		}
	}
	return false
}

func (b Bridge) Add(c Component) Bridge {
	b = Bridge(append([]Component(b), c))
	return b
}

func (b Bridge) Needs() int {
	t := []Component(b)
	c := t[len(t)-1]
	if len(t) == 1 {
		return c.Other(0)
	}
	c1 := t[len(t)-2]

	// Find the side of c that doesn't connect with c1
	if c.Has(c1.Side1) {
		return c.Other(c1.Side1)
	}
	return c.Other(c1.Side2)
}

func (b Bridge) Length() int {
	return len([]Component(b))
}

func (b Bridge) String() string {
	ret := "[ "
	for _, v := range []Component(b) {
		ret += v.Name + " "
	}
	return fmt.Sprint(ret+"(", b.Strength(), ";", b.Length(), ") ]")
}

type Component struct {
	Name         string
	Side1, Side2 int
}

func NewComponent(in string) Component {
	c := Component{}
	c.Name = in
	pts := strings.Split(in, "/")
	c.Side1 = Atoi(pts[0])
	c.Side2 = Atoi(pts[1])
	return c
}

func (c *Component) Equals(t Component) bool {
	return c.Side1 == t.Side1 && c.Side2 == t.Side2
}

func (c *Component) Strength() int {
	return c.Side1 + c.Side2
}

func (c *Component) Has(v int) bool {
	return c.Side1 == v || c.Side2 == v
}

func (c *Component) Other(v int) int {
	if c.Side1 == v {
		return c.Side2
	}
	return c.Side1
}

func (c *Component) String() string {
	return c.Name
}

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
}

func StdinToStrings() []string {
	var input []string
	scanner := bufio.NewScanner(os.Stdin)
	for scanner.Scan() {
		input = append(input, scanner.Text())
	}
	return input
}