Problem #17

Problem link
Solution:

package main

func main() {
    sum := 0
    for i := 0; i < 1000; i++ {
        sum += lengthNumber(i)
    }
    println(sum + len("onethousand"))
}

func lengthNumber(number int) int {
    switch number {
    case 0:
        return 0
    case 1:
        return 3 //one
    case 2:
        return 3 //two
    case 3:
        return 5 //three
    case 4:
        return 4 //four
    case 5:
        return 4 //five
    case 6:
        return 3 //six
    case 7:
        return 5 //seven
    case 8:
        return 5 //eight
    case 9:
        return 4 //nine
    case 10:
        return 3 //ten
    case 11:
        return 6 //eleven
    case 12:
        return 6 //twelve
    case 13:
        return 8 //thirteen
    case 14:
        return 8 //fourteen
    case 15:
        return 7 //fifteen
    case 16:
        return 7 //sixteen
    case 17:
        return 9 //seventeen
    case 18:
        return 8 //eighteen
    case 19:
        return 8 //nineteen
    case 20:
        return 6 //twenty
    case 30:
        return 6 //thirty
    case 40:
        return 5 //forty
    case 50:
        return 5 //fifty
    case 60:
        return 5 //sixty
    case 70:
        return 7 //seventy
    case 80:
        return 6 //eighty
    case 90:
        return 6 //ninety
    }
    if number < 100 {
        return lengthNumber(number-(number%10)) + lengthNumber(number%10)
    }
    if number%100 == 0 {
        return lengthNumber(number/100) + 7
    }
    return lengthNumber(number/100) + 10 + lengthNumber(number%100)
}

Result: 21124
Time: 0m0.003s