Sunday, 10 February 2013

Go-ing to Euler


Somewhere you have to start using a new language. I found it pretty frustrating to invent example code. You can cut corners or be negligent easily. That's why I really love Project Euler. I solved problems here already using many languages: PHP, C, Ruby, Python and Haskell.


It's really either for beginning something or math nerds :) Solving problems I was curious how much of Go's specialties I can use at the beginning. Fortunately there was some, such as the multiple return arguments, or simple variable definition, the dynamic type assignment - or anonym function, as much as it's a specialty, though.

The compiler was pretty helpful telling me where the problems are and what are they. Sublime has Go syntax highlighter so that was my choice of editor.

As a Sunday night bedtime story here you are my first three solutions.

#1


If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000.


package main

import "fmt"

func main() {
  sum := 0
  for i := 3; i < 1000; i++ {
    if i % 3 == 0 || i % 5 == 0 {
      sum += i
    }
  }
  fmt.Println(sum)
}

#2


Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:

1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...

By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.


package main

import "fmt"

func main() {
  var sum, prev, current uint32 = 0, 0, 1

  micfib := func(prev, current uint32) (uint32, uint32) {
    return current, current + prev
  }

  for current < 4e6 {
    prev, current = micfib(prev, current)

    if current % 2 == 0 {
      sum += current
    }
  }

  fmt.Println(sum)
}

#3


The prime factors of 13195 are 5, 7, 13 and 29.

What is the largest prime factor of the number 600851475143 ?


package main

import "fmt"

func main() {
  var div, max uint64 = 2, 600851475143

  for div < max {
    if max % div == 0 {
      max /= div
      div = 2
    } else {
      div++
    }
  }

  fmt.Println(div)
}


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This weekend I had almost zero time to care about my topics. I really hope soon I'll find some time to dig deeper into Go. I kinda like it, to be honest.

Peter

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