Problem #47

Problem link
Solution:

package main

func main() {
    arr := make([]bool, 1000000)
    arr[0], arr[1] = true, true
    count, prime := 2, 3
    var k int
    for {
        for k = 2 * prime; k < len(arr); k += prime {
            arr[k] = true
        }
        for k = prime + 2; k < len(arr) && arr[k]; k += 2 {
        }
        if k < len(arr) {
            prime = k
            count++
        } else {
            break
        }
    }
    primes := make([]int, count)
    primes[0] = 2
    index := 1
    for i := 3; i < len(arr); i += 2 {
        if !arr[i] {
            primes[index] = i
            index++
        }
    }
    var consecutiveCount, divisorCount, tmp int
outer:
    for i := 646; i < 1000000; i++ {
        consecutiveCount = 0
    inner:
        for j := i; j < i+4; j++ {
            divisorCount = 0
            //find divisors of j
            if !arr[j] && j%2 != 0 {
                //a quick check: if j is prime
                continue outer
            } else {
                tmp = j
                for k := 0; k < len(primes); k++ {
                    if (!arr[tmp] && tmp%2 != 0) || tmp%primes[k] == 0 {
                        divisorCount++
                        if divisorCount == 4 {
                            consecutiveCount++
                            if consecutiveCount == 4 {
                                println(i)
                                return
                            }
                            continue inner
                        } else if !arr[tmp] && tmp%2 != 0 {
                            //another quick check for prime tmp
                            continue outer
                        }
                        for tmp%primes[k] == 0 {
                            tmp /= primes[k]
                        }
                    }
                }
            }
        }
    }
}

Result: 134043
Time: 0m1.323s