Problem #32

Problem link
Solution:

package main

import (
    "strconv"
    "strings"
)

func main() {
    mp := map[int]int{}
    for i := 1; i < 200; i++ {
        for j := 1; j < 5000; j++ {
            if isPandigital(i, j, i*j) {
                mp[i*j] = 1
            }
        }
    }
    sum := 0
    for key, _ := range mp {
        sum += key
    }
    println(sum)
}

func isPandigital(mul1, mul2, result int) bool {
    str := strconv.Itoa(mul1) + strconv.Itoa(mul2) + strconv.Itoa(result)
    if len(str) != 9 {
        return false
    }
    for i := 1; i < 10; i++ {
        if !strings.Contains(str, strconv.Itoa(i)) {
            return false
        }
    }
    return true
}

Result: 45228
Time: 0m2.405s

Problem #38

Problem link
Solution:

package main

import (
    "strconv"
    "strings"
)

func main() {
    max := 0
    var tmp int
    for i := 1; i < 10000; i++ {
        str := ""
        for j := 1; j < 9 && len(str) < 9; j++ {
            str += strconv.Itoa(i * j)
        }
        if len(str) == 9 && isPandigital(str) {
            tmp, _ = strconv.Atoi(str)
            if tmp > max {
                max = tmp
            }
        }
    }
    println(max)
}

func isPandigital(str string) bool {
    if len(str) != 9 {
        return false
    }
    for i := 1; i < 10; i++ {
        if !strings.Contains(str, strconv.Itoa(i)) {
            return false
        }
    }
    return true
}

Result: 932718654
Time: 0m0.049s

Problem #41

Problem link
Solution:

package main

import (
    "strconv"
    "strings"
)

func main() {
    a := make([]bool, 87654322)
    a[0], a[1] = true, true
    prime := 3
    var k int
    finished := false
    for !finished {
        for k = 2 * prime; k < len(a); k += prime {
            a[k] = true
        }
        for k = prime + 2; k < len(a) && a[k]; k += 2 {
        }
        if k < len(a) {
            prime = k
        } else {
            finished = true
        }
    }
    //a now has false values for the primes and multiples of 2
    //but we skip even numbers in our iteration.
    for i := int64(87654321); i > 0; i -= 2 {
        if !a[i] && isPandigital(i) {
            println(i)
            return
        }
    }
}

func isPandigital(in int64) bool {
    str := strconv.Itoa64(in)
    n := len(str)
    for i := 1; i <= n; i++ {
        if !strings.Contains(str, strconv.Itoa(i)) {
            return false
        }
    }
    return true
}

Result: 7652413
Time: 0m15.596s

Problem #43

Problem link
Solution:

package main

import (
    "strconv"
)

var result int64
var divisors []int
var tmp int
var tmp64 int64

func main() {
    result = int64(0)
    divisors = []int{2, 3, 5, 7, 11, 13, 17}
    allPerms("", "0123456789")
    println(result)
}

func allPerms(pre, s string) {
    if len(s) == 0 {
        checkTheProperty(pre)
    } else {
        for i := 0; i < len(s); i++ {
            allPerms(pre+s[i:i+1], s[0:i]+s[i+1:len(s)])
        }
    }
}

func checkTheProperty(s string) {
    if s[0] == '0' {
        return
    } else {
        for i := 1; i < 8; i++ {
            if tmp, _ = strconv.Atoi(s[i : i+3]); tmp%divisors[i-1] != 0 {
                return
            }
        }
    }
    tmp64, _ = strconv.Atoi64(s)
    result += tmp64
}

Result: 16695334890
Time: 0m6.223s