Problem 49: Prime Permutations

The arithmetic sequence, 1487, 4817, 8147, in which each of the terms increases by 3330, is unusual in two ways: (i) each of the three terms are prime, and, (ii) each of the 4-digit numbers are permutations of one another.

There are no arithmetic sequences made up of three 1-, 2-, or 3-digit primes, exhibiting this property, but there is one other 4-digit increasing sequence.

What 12-digit number do you form by concatenating the three terms in this sequence?

Here is my solution in Golang.

////////////////////////////////////////////////////////////////////////////////
package main

////////////////////////////////////////////////////////////////////////////////
import (
	"fmt"
	"sort"
)

////////////////////////////////////////////////////////////////////////////////
func main() {
	sieve := sieveOfErastothenes(10000)

	for i := 1000; i <= 9999; i++ {
		if sieve[i] == false {
			for j := 1; i+(2*j) <= 9999; j++ {
				if !(sieve[i+j]) && !(sieve[i+(2*j)]) {
					if permCheck(i, i+j, i+(2*j)){
						fmt.Printf("Prime permutation sequence: %d%d%d\n", i, i+j, i+(2*j))
					}
				}
			}
		}
	}
}

////////////////////////////////////////////////////////////////////////////////
func sieveOfErastothenes(maxVal int) []bool {
	sieve := make([]bool, maxVal)

	for i := 2; i < 10000; i++ {
            if(sieve[i] == false){
		for j := i * 2; j < (10000 - i); j += i {
			sieve[j] = true
		}
            }
	}
	return sieve
}

////////////////////////////////////////////////////////////////////////////////
func digSepSort(a int) (digBuff []int) {
	for a != 0 {
		modBuff := (a % 10)
		a /= 10
		digBuff = append(digBuff, modBuff)
	}
	sort.Ints(digBuff)
	return digBuff
}

////////////////////////////////////////////////////////////////////////////////
func permCheck(a int, b int, c int) bool {
	digBuffA := digSepSort(a)
	digBuffB := digSepSort(b)
	digBuffC := digSepSort(c)

	for i := 0; i < 4; i++ {
		if digBuffA[i] != digBuffB[i] {
			return false
		}
		if digBuffB[i] != digBuffC[i] {
			return false
		}
	}

	return true
}
////////////////////////////////////////////////////////////////////////////////