sieve_of_eratosthenes.go

package main

import (
	"fmt"
	"math"
	"os"
	"strconv"
)

func main() {

	// Find bigger prime <= N
	N, _ := strconv.Atoi(os.Args[1])
	table := make([]bool, N+1)
	table[0] = true
	table[1] = true
	M := int(math.Sqrt(float64(N))) + 1
	for i := 2; i <= M; i++ {
		if table[i] {
			continue
		}
		for j := (i * i); j <= N; j += i {
			table[j] = true
		}

	}
	for i := N; ; i-- {
		if !table[i] {
			fmt.Println(i)
			break
		}
	}

}