0011 - Project Euler

// 0011.go contains some functions to solve ProjectEuler.net's Problem #11
// https://projecteuler.net/problem=11
package main

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

// MaxNumber returns the maximum number in an int array of numbers
func MaxNumber(numbers []int) int {
    max := 0

    for _,i := range numbers {
        if i > max {
            // Replace max with i
            max = i
        }
    }

    // Return maximum number
    return max
}

// Make2DIntArray returns a 2D array given a multi-line string of numbers.
func Make2DIntArray(numberString string) [][]int {
    // Split the string by linebreaks
    stringArray := strings.Split(numberString, "\n")
    intArray := make([][]int, len(stringArray))

    for i,v := range(stringArray) {
        // Split each line into separate strings
        splitString := strings.Split(v, " ")
        // Create a new array for this particular line
        splitStringArray := make([]int, len(splitString))

        for j, s := range splitString {
            // Convert each element to number and add to line array
            splitStringArray[j],_ = strconv.Atoi(s)
        }

        // Add line array to main int array
        intArray[i] = splitStringArray
    }

    // Return result
    return intArray
}

// GetMaxAdjacentProduct returns the maximum product of a number of
// adjacent numbers in any direction (vertical, horizontal, diagonal)
// in a 2D int array
func GetMaxAdjacentProduct(adjNumbers int, intArray [][]int) int {
    // Initialise variables
    maxProduct := 0
    x := len(intArray)
    y := len(intArray[0])
    var testMaxProduct int


    for i := 0; i<x; i++ {
        OUTER:
        for j := 0; j<y; j++ {
            // Create variables to store products of each direction
            horizontal := 1
            diagonal := 1
            vertical := 1
            revdiagonal := 1

            for k := 0; k<adjNumbers; k++{
                if j+k >= y || i+k >= x || i-k < 0 || intArray[i+k][j+k] == 0 ||
                intArray[i-k][j+k] == 0 {
                    // Impossible values
                    continue OUTER
                }

                // Append to directional product values
                diagonal *= intArray[i+k][j+k]
                horizontal *= intArray[i][j+k]
                vertical *= intArray[i+k][j]
                revdiagonal *= intArray[i-k][j+k]
            }

            // Get current iteration's max product number
            testMaxProduct = MaxNumber([]int{diagonal, horizontal, vertical, revdiagonal})

            if testMaxProduct > maxProduct {
                // Replace max product with new highest product (this iteration)
                maxProduct = testMaxProduct
            }
        }
    }

    // Return the max product
    return maxProduct
}

func main(){
    // Display result
    intString := `08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08
    49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00
    81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65
    52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91
    22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80
    24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50
    32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70
    67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21
    24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72
    21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95
    78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92
    16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57
    86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58
    19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40
    04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66
    88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69
    04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36
    20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16
    20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54
    01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48`

    fmt.Println(GetMaxAdjacentProduct(4, Make2DIntArray(intString)))
}