2019 Day 14 Complete

2019/day14/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"math"
 	"strings"
 
 	helpers "git.bullercodeworks.com/brian/adventofcode/helpers"
@@ -29,6 +30,64 @@ func part1(inp []string) {
 }
 
 func part2(inp []string) {
+	fuel := GetMaxFuelForOre(inp, 1000000000000)
+	fmt.Println("# Part 2")
+	fmt.Println("Fuel:", fuel)
+}
+
+func FindRequiredOre(inp []string, fuel int) int {
+	allReactions := make(map[string]*Reaction)
+	for _, v := range inp {
+		r := NewReaction(v)
+		allReactions[r.out] = r
+	}
+	return Produce("FUEL", fuel, allReactions, make(map[string]int))
+}
+
+func Produce(chem string, amt int, allReactions map[string]*Reaction, excess map[string]int) int {
+	if chem == "ORE" {
+		return amt
+	}
+	if excess[chem] >= amt {
+		excess[chem] -= excess[chem]
+		excess[chem] = 0
+	}
+	recipe := allReactions[chem]
+	times := int(math.Ceil(float64(amt) / float64(recipe.outQty)))
+	ret := 0
+	for k, inAmt := range recipe.in {
+		ret += Produce(k, inAmt*times, allReactions, excess)
+	}
+	numProduced := times * recipe.outQty
+	excess[chem] += numProduced - amt
+	return ret
+}
+
+func GetMaxFuelForOre(inp []string, ore int) int {
+	var start, guesses, lastGuess, fuelGuess int
+	end := ore
+	for {
+		guesses++
+		fuelGuess = (end-start)/2 + start
+		requiredOre := FindRequiredOre(inp, fuelGuess)
+		if requiredOre == ore {
+			break
+		}
+		if requiredOre > ore {
+			end = fuelGuess
+		} else {
+			start = fuelGuess
+		}
+		if fuelGuess == lastGuess {
+			break
+		}
+		lastGuess = fuelGuess
+	}
+	return fuelGuess
+}
+
+// this is too slow... Gonna re-engineer it...
+func part2Slow(inp []string) {
 	allReactions = make(map[string]*Reaction)
 	for _, v := range inp {
 		r := NewReaction(v)