R: find largest common substring starting at the beginning

Question

I\'ve got 2 vectors:

word1 <- \"bestelling\"   
word2 <- \"bestelbon\"

Now I want to find the largest common substring that starts at the

Answer 1

flodel <- function(word1, word2) {
   # the length of the shorter word
   n <- min(nchar(word1), nchar(word2))
   # two vectors of characters of the same length n
   c1 <- strsplit(word1, "", fixed = TRUE)[[1]][1:n]
   c2 <- strsplit(word2, "", fixed = TRUE)[[1]][1:n]
   # a vector that is TRUE as long as the characters match
   m <- as.logical(cumprod(c1 == c2))
   # the answer
   paste(c1[m], collapse = "")
}