Project Euler — problem 8

tmp <- scan("tmp.txt", what = "")  # store the numbers in tmp.txt
tmp <- paste(tmp, collapse = "")  # get the single number
num.lst <- strsplit(tmp, split = "")  # split it into 1-digit numbers
num.lst <- as.numeric(unlist(num.lst))
products <- num.lst[1:(n - 4)] * num.lst[2:(n - 3)] * num.lst[3:(n - 2)] * 
            num.lst[4:(n - 1)] * num.lst[5:n]
result <- max(products)
cat("The result is:", result, "\n")

max.prod <- function(x) {  
  # helper to calculate the largest product in a give number sequence x
  lst <- strsplit(x, split = "")
  lst <- as.numeric(unlist(lst))
  n <- length(lst)
  products <- lst[1:(n - 4)] * lst[2:(n - 3)] * lst[3:(n - 2)] * 
              lst[4:(n - 1)] * lst[5:n]
  max.product <- max(products)
  return(max.product)
}
num.lst <- strsplit(tmp, split = "[0-1]")
num.lst <- unlist(num.lst)
mt <- nchar(num.lst) >= 5  # remove small number sequences
num.lst <- as.list(num.lst[mt])  # coerce to list for the next step using sapply()
result <- max(sapply(num.lst, max.prod))
cat("The result is:", result, "\n")