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main.go
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main.go
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package main
import (
"log"
"os"
"strconv"
"github.com/TomasCruz/projecteuler"
)
/*
Largest prime factor
Problem 3
The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143 ?
*/
func main() {
var limit int64
if len(os.Args) > 1 {
var err error
limit, err = strconv.ParseInt(os.Args[1], 10, 64)
if err != nil {
log.Fatal("bad argument")
}
} else {
limit = 600851475143
}
projecteuler.Timed(calc, limit)
}
func calc(args ...interface{}) (result string, err error) {
limit := args[0].(int64)
var largest int
inspected := int(limit)
projecteuler.Primes(inspected/2+1, isDivisibleToOne, &inspected, &largest)
if largest == 0 {
largest = int(limit)
}
result = strconv.Itoa(largest)
return
}
func isDivisibleToOne(args ...interface{}) bool {
inspected := args[0].(*int)
largest := args[1].(*int)
divider := args[2].(int)
for *inspected%divider == 0 {
*largest = divider
*inspected /= divider
}
return *inspected == 1
}