in Programming |

Project Euler Problem 1 Solution: Clojure

After PhillyETE, I wanted to try out some Clojure, so I decided to solve the first problem of Project Euler. I coded up my own solution using some of the references on the Clojure site.

Project Euler Problem Description, from Project Euler

Find the sum of all the multiples of 3 or 5 below N. (N is 1000 is this Project Euler problem.)

Solutions

My first attempt

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
(def nmbrs (range 0 1000))
(def multiples
    (filter
        #(and
            (not= % 0)
            (or
                (=
                    (rem % 3)
                    0
                    )
                (=
                    (rem % 5)
                    0
                    )
                )
            )
        nmbrs
        )
    )
(reduce + multiples)

Another attempt by a different author

Afterwards, I came across a terser, more elegant solution on a site that seems to have had the same idea as I did, Learning Clojure with Project Euler. The site had a really elegant looking solution:

?
1
2
3
4
5
6
; //grok-code.com/367/learning-clojure-with-project-euler/
(defn problem01 [limit]
 (reduce + (filter #(or (zero? (mod % 3))
                        (zero? (mod % 5)))
                   (take (- limit 1) (iterate inc 1)))))
(problem 1000)

My revised attempt

The use of take and iterate are really interesting. I haven’t encountered these “lazy” functions, and was surprised when I tried to run (iterate inc 1) in the REPL. I decided to modify my version with some of the things I learned from the version above, and make it more terse.

?
1
2
3
4
5
6
7
8
9
10
11
(defn problem01
    [upper]
    (reduce +
        (filter
            #(or
                (zero?(rem % 3))
                (zero?(rem % 5))
                )
            (range 1 upper)
            ))
    )

I’ll be working on some more of the problems in the coming days.

(PS. If you are wondering why I use rem instead of mod, it’s because I am using an older version of clojure with TextMate–I’ve yet to upgrade)

  3. Cool, I will keep that in mind. I am currently using a clojure version that came with a TextMate bundle. Unfortunately, there are no instructions to upgrade. I’m going to keep trying though.

Comments are closed.