Merging list of numbers in R - r

Question

I've a list with groups of numbers as follows:
myList <- list(1:5, c(1,3,4,7), 2:6, c(3,6:9), 4:8)
myList
#[[1]]
#[1] 1 2 3 4 5
#
#[[2]]
#[1] 1 3 4 7
#
#[[3]]
#[1] 2 3 4 5 6
#
#[[4]]
#[1] 3 6 7 8 9
#
#[[5]]
#[1] 4 5 6 7 8
So we have 5 groups of numbers in myList. I want to merge two groups if they have at least s% same numbers in them. I compute similarity using the following function call:
get.Overlap <- function(group_A, group_B)
{
common <- length(intersect(group_A, group_B))
minimum_length <- min(length(group_A), length(group_B))
#formula: |A ^ B| / min{|A|, |B|}
overlap_score <- common / minimum_length
overlap_score
}
I have implemented mergeList(myList, threshold_s) using loops as follows:
mergeList <- function(myList, threshold_s)
{
returnList <- list()
i <- 1
while(i <= length(myList))
{
thisList <- myList[[i]]
j <- i + 1
while(j <= length(myList))
{
tempList <- myList[[j]]
if(get.Overlap(thisList, tempList) >= threshold_s)
{
thisList <- union(thisList, tempList)
myList[[j]] <- NULL
}
else
{
j <- j + 1
}
}
returnList <- c(returnList, list(thisList))
i <- i + 1
}
returnList
}
Now if I call merge(myList, threshold_s), where threshold_s is set to 0.80 meaning 80% similarity, the output will be
#[[1]]
#[1] 1 2 3 4 5 6
#
#[[2]]
#[1] 1 3 4 7
#
#[[3]]
#[1] 3 4 6 7 8 9
The complexity is comparatively high. I am looking for a fast implement of merge(myList, threshold_s) for a large list, say length of myList may be around 50,000.
Thanks in advance.