Question

How to find the largest prime factor of a number in Go

Answer 1

package main

import (
    "fmt"
)

func largestPrimeFactor(n int) int {
    div := 2
    maxPFact := -1

    for n != 0 {
        if n%div != 0 {
            div++
        } else {
            maxPFact = n
            n /= div // Integer division
            if n == 1 {
                break
            }
        }
    }

    return maxPFact
}

func main() {
    fmt.Println(largestPrimeFactor(124))  // 2 x 2 x 31
    fmt.Println(largestPrimeFactor(288))  // 2 x 2 x 2 x 2 x 2 x 3 x 3
    fmt.Println(largestPrimeFactor(1288)) // 2 x 2 x 2 x 7 x 23
    fmt.Println(largestPrimeFactor(100000000)) // 2, 2, 2, 2, 2, 2, 2, 2, 5, 5, 5, 5, 5, 5, 5, 5
}



/*
run:

31
3
23
5

*/

 

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