AoC-2015-Day4

main.go

package main

import (
        "crypto/md5"
        "fmt"
        "math"
        "sort"
        "strconv"
        "sync"
        "time"
)


func AdventCoinMiner(secretKey, goal string, ind, bound int, ch chan int, wg *sync.WaitGroup) {
        // fmt.Printf("Goroutine: %d\n", ind)
        defer wg.Done()
        min := ind * bound
        max := bound + min
        length := len(goal)
        // fmt.Printf("min: %d, max: %d\n", min, max)
        for i := min; i <= max; i++ {
                hashInput := []byte(secretKey + strconv.Itoa(i)) //"abcdef1000000"
                md5Sum := md5.Sum(hashInput)
                if fmt.Sprintf("%x", md5Sum)[:length] == goal {
                        ch <- i
                        return
                }
        }
        ch <- 0
        return
}

func main() {
        start := time.Now()
        secretKey := "iwrupvqb"
        zeros := "00000"
        bound := int(math.Pow10(len(secretKey) - 1))
        bin := int(bound/len(secretKey))
        ch := make(chan int, len(secretKey))
        wg := new(sync.WaitGroup)
        wg.Add(len(secretKey))
        fmt.Println("bound: ", bound)
        fmt.Println("bin: ", bin)
        for i := 0; i < len(secretKey); i++ {
                go AdventCoinMiner(secretKey, zeros, i , bin, ch, wg)
        }
        defer close(ch)
        returnedValues := make([]int,0)
        for i := 0; i < len(secretKey); i++ {
                val := <- ch
                if val > 0 {
                        returnedValues = append(returnedValues, val)
                }
        }
        sort.Ints(returnedValues)
        fmt.Println("Value: ", returnedValues[0])
        elapsed := time.Since(start)
        fmt.Println("Elapsed Time: ", elapsed)
}

main3.go

// Brute Force linear Search over 10^(len(secretKey) - 1))
package main

import (
        "crypto/md5"
        "fmt"
        "math"
        "strconv"
        "time"
)


func AdventCoinMiner(secretKey, goal string) int {
        bound := int(math.Pow10(len(secretKey) - 1))
        length := len(goal)
                fmt.Println("bound: ", bound)
        for i := 0; i < bound; i++ {
                hashInput := []byte(secretKey + strconv.Itoa(i)) //"abcdef1000000"
                md5Sum := md5.Sum(hashInput)
                if fmt.Sprintf("%x", md5Sum)[:length] == goal {
                        return i
                }
        }
                return -1
}

func main() {
        start := time.Now()
        secretKey := "iwrupvqb"
        zeros := "000000"

                value := AdventCoinMiner(secretKey, zeros)
        fmt.Println("Value: ", value)
        elapsed := time.Since(start)
        fmt.Println("Elapsed Time: ", elapsed)
}

Updated

using sync.WaitGroup for the Miner task will be able to provide either the actual iteration value (if found) or 0 if not found.

Using the same amount of listeners on the channels as goroutines + waitgroups one can determine the iteration value.