CODEWITHSUNDEEP
rgreatest-common-divisor
himalaya
himalaya

Reputation: 25

How to find GCD for a list of (1:n) numbers in R

How to find GCD for a list of (1:n) numbers in R ?

GCD=function(a, b){
m=min(a, b)
while(a%%m>0|b%%m>0){m=m-1}
return(m)}

Here is my code to find GCD for two integers, how can I modify it to find GCD for a list of numbers from 1 to n without too much changes on my original code? Thankyou very much !

Upvotes: 0

Views: 663

Answers (2)

ThomasIsCoding
ThomasIsCoding

Reputation: 102261

You can define function gcd based on GCD like below

gcd <- function(...) Reduce(GCD,list(...))

and you can try

> gcd(6, 24, 28, 36, 200)
[1] 2

If you want a recursion for GCD (your origin answer has a slow convergence due to m <- m -1), you can try

GCD <- function(...) {
    args <- c(...)
    if (length(args) == 2) {
        if (args[2] == 0) {
            return(args[1])
        } else {
            return(Recall(args[2], args[1] %% args[2]))
        }
    }
    Recall(args[1], Recall(args[-1]))
}

such that

> GCD(6, 24, 28, 36, 200)
[1] 2

> GCD(12, 24, 28, 36, 200)
[1] 4

Upvotes: 2

bouncyball
bouncyball

Reputation: 10771

You can use the any function:

GCD <- function(x) {
  m = min(x)
  
  while (any(x %% m > 0)){
    m = m - 1
  }
  
  return(m)
}

GCD(c(12, 24, 28, 36, 200))
# [1] 4

GCD(c(6, 24, 28, 36, 200))
# [1] 2

Upvotes: 2

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