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alexchao26
103 lines
3.2 KiB
Go
103 lines
3.2 KiB
Go
package main
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import (
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"github.com/alexchao26/advent-of-code-go/util"
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"fmt"
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"strconv"
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"strings"
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)
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func main() {
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input := util.ReadFile("../input.txt")
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stoichiometryGraph := makeDependencyGraph(strings.Split(input, "\n"))
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neededChemicals := map[string]int{"FUEL": 1}
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// fmt.Println(stoichiometryGraph, neededChemicals)
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// while the neededChemicals map has positive values for keys besides "ORE"
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for !isOnlyOres(neededChemicals) {
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// iterate through neededChemicals
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for neededChemical, quantityNeeded := range neededChemicals {
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// if a positive value is found for a neededChemical besides "ORE"
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if quantityNeeded > 0 && neededChemical != "ORE" {
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// find its reaction in the stoichiometryGraph
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reactionStoichiometry := stoichiometryGraph[neededChemical]
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// determine the number of times the reactionStoichiometry must be run
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timesToRun := quantityNeeded / reactionStoichiometry[neededChemical]
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if quantityNeeded%reactionStoichiometry[neededChemical] > 0 {
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timesToRun++
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}
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// decrement all of the values in neededChemicals map with this reaction's details (* timesToRun)
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for reactionChemical, chemicalStoich := range reactionStoichiometry {
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neededChemicals[reactionChemical] -= chemicalStoich * timesToRun
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}
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}
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}
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}
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// Print final output
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fmt.Println("ORE needed", neededChemicals["ORE"])
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}
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// Creates a graph that maps the products name to its full reaction stoichiometry
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func makeDependencyGraph(reactions []string) map[string]map[string]int {
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graph := make(map[string]map[string]int)
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for _, reaction := range reactions {
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product, reactionStoichiometry := parseReaction(reaction)
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graph[product] = reactionStoichiometry
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}
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return graph
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}
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// parseReaction takes in a line of the input i.e. a reaction in a string
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// parses all its details and returns the generated product as a string
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// and a map of all products to the quantity used/produced by the reaction
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// for produced chemicals, map value will be > 0, inputs will be < 0
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func parseReaction(reaction string) (string, map[string]int) {
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reactionStoichiometry := make(map[string]int)
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splitByArrow := strings.Split(reaction, " => ")
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productStr := splitByArrow[1]
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reactantsStr := splitByArrow[0]
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// handle product
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productQty, productName := parseQtyAndName(productStr)
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reactionStoichiometry[productName] = productQty
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// split reactants via comma first
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reactantsSli := strings.Split(reactantsStr, ", ")
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for _, str := range reactantsSli {
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reactantQuantity, reactantName := parseQtyAndName(str)
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reactionStoichiometry[reactantName] = -1 * reactantQuantity
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}
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return productName, reactionStoichiometry
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}
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// parse an inputted string of the for "<number> <string>" and return the int & string
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func parseQtyAndName(input string) (int, string) {
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split := strings.Split(input, " ")
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quantity, _ := strconv.Atoi(split[0])
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name := split[1]
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return quantity, name
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}
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// helper function to determine if the neededChemicals graph is "complete"
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// it is complete if there only positive value is for the chemical "ORE"
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func isOnlyOres(neededChemicals map[string]int) bool {
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for key, val := range neededChemicals {
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if key != "ORE" && val > 0 {
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return false
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}
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}
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return true
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}
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