0008 - Project Euler

// 0008.go contains some functions to solve ProjectEuler.net's Problem #8
// https://projecteuler.net/problem=8
package main

import (
    "fmt"
    "strings"
    "strconv"
)

// StringToIntArray converts a number string to an int array, assuming all
// elements in the string array were numbers to begin with.
func StringToIntArray(numberString string) []int {
    // Create int array
    intArray := make([]int, len(numberString))
    // Strip whitespace in numberString and convert to string array
    stringArray := strings.Split(strings.Join(strings.Fields(numberString), ""), "")

    for i, s := range stringArray {
        // Convert string to int and add to int array
        intArray[i], _ = strconv.Atoi(s)
    }

    // Return result
    return intArray
}

// AdjacentProduct returns the highest product in an array given the number
// of consecutive digits and the int array.
func AdjacentProduct(digits int, intArray []int) int {
    // Initialise variables
    maxProduct := 0
    length := len(intArray)-digits
    var currentProduct int

    OUTER:
    for i := 0; i<length; i++ {
        currentProduct = 1

        for j := 0; j < digits; j++ {
            if intArray[i+j] == 0 {
                // Anything * 0 is equal to 0, and irrelevant
                i += digits-1
                continue OUTER
            }

            // Calculate product
            currentProduct *= intArray[i+j]
        }

        if currentProduct > maxProduct {
            // Get highest possible product
            maxProduct = currentProduct
        }
    }

    return maxProduct
}

func main(){
    // Answer the problem
    number := `73167176531330624919225119674426574742355349194934
    96983520312774506326239578318016984801869478851843
    85861560789112949495459501737958331952853208805511
    12540698747158523863050715693290963295227443043557
    66896648950445244523161731856403098711121722383113
    62229893423380308135336276614282806444486645238749
    30358907296290491560440772390713810515859307960866
    70172427121883998797908792274921901699720888093776
    65727333001053367881220235421809751254540594752243
    52584907711670556013604839586446706324415722155397
    53697817977846174064955149290862569321978468622482
    83972241375657056057490261407972968652414535100474
    82166370484403199890008895243450658541227588666881
    16427171479924442928230863465674813919123162824586
    17866458359124566529476545682848912883142607690042
    24219022671055626321111109370544217506941658960408
    07198403850962455444362981230987879927244284909188
    84580156166097919133875499200524063689912560717606
    05886116467109405077541002256983155200055935729725
    71636269561882670428252483600823257530420752963450`

    numberArray := StringToIntArray(number)

    fmt.Println(AdjacentProduct(13, numberArray))
}