Homework 3

homeworks/Vitalii.Timolianov-XX-NF-XX/Homework3/main.go

@@ -0,0 +1,133 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"sync"
+
+	flag "github.com/spf13/pflag"
+)
+
+var defaultOrder = []uint{1, 2, 1, 3, 4}
+var defaultState = "[[1,1,2,3],[2,3,4],[1,3],[5,4,3],[2,2,1]]"
+
+// Products - slice of products
+type Products []uint
+
+// Machines - slice of machines with products
+type Machines []Products
+
+// Converts JSON state string to Machines
+func getMachinesFromState(state *string) Machines {
+	var stateBytes = []byte(*state)
+	var machines Machines
+
+	err := json.Unmarshal(stateBytes, &machines)
+
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(3)
+	}
+
+	return machines
+}
+
+// Converts parameters to valid data
+func parseFlags() (Products, Machines) {
+	var order *[]uint = flag.UintSlice("order", defaultOrder, "Order to fulfill e.g.: {4,1}")
+	var rawState *string = flag.String("state", defaultState, "Current state of vending machines e.g.: [[1,2],[4,3]]")
+
+	flag.Parse()
+
+	machines := getMachinesFromState(rawState)
+	products := Products(*order)
+
+	return products, machines
+}
+
+// Closes channel when wait group is done (I don't like it, but it works)
+func closeOnDone(c chan Machines, waitgroup *sync.WaitGroup) {
+	waitgroup.Wait()
+	close(c)
+}
+
+// Makes shallow copy of Machines without first element at 'index'
+func (machines Machines) copyWithout(index int) Machines {
+	newMachines := make(Machines, len(machines))
+
+	for i, m := range machines {
+		if i == index {
+			newMachines[i] = m[1:]
+			continue
+		}
+		newMachines[i] = m
+	}
+
+	return newMachines
+}
+
+// Finds the top order product in machines
+// All the logic/magic happens here
+func findProduct(order Products, machines Machines, c chan Machines, waitgroup *sync.WaitGroup) {
+	defer waitgroup.Done()
+
+	orderedProduct := order[0]
+	for i, m := range machines {
+		if len(m) == 0 {
+			continue
+		}
+
+		if m[0] == orderedProduct {
+			reducedMachines := machines.copyWithout(i)
+			orderRest := order[1:]
+
+			if len(orderRest) == 0 {
+				c <- reducedMachines
+				return
+			}
+
+			waitgroup.Add(1)
+			go findProduct(orderRest, reducedMachines, c, waitgroup)
+		}
+	}
+}
+
+// Tries to resolve order and return possible states of vending machines
+func (machines Machines) getOrderSolutions(order Products) ([]Machines, bool) {
+	var waitgroup sync.WaitGroup
+	var possibleStates = []Machines{}
+
+	c := make(chan Machines, 8)
+
+	waitgroup.Add(1)
+	go findProduct(order, machines, c, &waitgroup)
+	go closeOnDone(c, &waitgroup)
+
+	for m := range c {
+		possibleStates = append(possibleStates, m)
+	}
+
+	ok := len(possibleStates) > 0
+	return possibleStates, ok
+}
+
+// Yep, this is where the whole thing starts
+func main() {
+	order, machines := parseFlags()
+	fmt.Printf("order: %v\n", order)
+	fmt.Printf("state: %v\n\n", machines)
+
+	possibleStates, ok := machines.getOrderSolutions(order)
+	if !ok {
+		fmt.Printf("This order cannot be fulfilled!\n")
+		os.Exit(1)
+	}
+
+	fmt.Printf("Order can be fulfilled in %v way(s).\n", len(possibleStates))
+	fmt.Printf("\nPossible vending machine states after fulfillment:\n")
+
+	for i, s := range possibleStates {
+		fmt.Printf("#%v %v\n", i+1, s)
+	}
+}