R/day-02.R

In shamindras/adventofcode2017:

#' For a given input list of vectors, calculate sum of all their ranges
#' Used in Day-02 of the Advent of Code 2017
#'
#' @param list_num_vec (list) : list of numeric vectors
#'
#' @export
get_range_numvec <- function(list_num_vec){
    list_num_vec %>%
        purrr::map(range) %>%
        purrr::map(diff) %>%
        base::unlist() %>%
        sum(na.rm = TRUE) %>%
        base::return()
}

#' For a given txt file containing rows of  numbers, calculates the sum
#' of their ranges
#' Used in Day-02 of the Advent of Code 2017
#' @param txt_file_path (character) : The path to the valid Day-02 input txt
#' file
#'
#' @export
get_range_txtfile <- function(txt_file){
    txt_file %>%
        adventofcode2017::parse_txtfile(txt_file = .
                                        , sep = "\t"
                                        , map_fun = as.numeric) %>%
        get_range_numvec(list_num_vec = .) %>%
        base::return()
}


#' Returns the first time an element divides another in an integer vector
#'
#' @param num_vec (integer) : An integer vector
#'
#' @export
get_even_divisor <- function(num_vec){

    num_vec <- base::as.integer(num_vec)

    # Set the dummy value of no divisor found to be -99
    DEFAULT_EMPTY_DIVISOR_OUT <- -99

    # Initialize the output of whole number divisors and no divisors
    whole_divisors <- base::integer()
    no_divisors    <- base::integer()

    for(i in seq_along(num_vec)){

        divisor <- num_vec[i]
        div_vec <- num_vec[-i]
        out_division <- div_vec %% divisor

        # Get the index of whole divisors
        # Set the dummy value of no whole divisor found to be -1
        div_idx0 <- ifelse(base::length(which(out_division == 0)) > 0
                           , base::which(out_division == 0)
                           , -1)

        # If a whole divisor is found then increment our whole divisor
        # vector
        if(div_idx0 != -1){
            whole_divisors <- c(whole_divisors
                                , div_vec[min(div_idx0)]/divisor)
        } else{
            # Increment by the dummy division value
            no_divisors <- c(no_divisors
                             , DEFAULT_EMPTY_DIVISOR_OUT)
        }
    }

    # We want to return the first whole divisor or the dummy value of -99
    # In the Advent of Code 2017, we should always hit this value
    out_val <- base::ifelse(base::length(whole_divisors) > 0
                            , whole_divisors[1]
                            , no_divisors[1])
    base::return(out_val)
}

#' Returns sum of all even division values from a collection of integer vectors
#'
#' @param txt_file (character) : A text file containing tab separated integer
#' values split across new lines for each vector
#'
#' @export
get_even_divisor_txtfile <- function(txt_file){
    txt_file %>%
        adventofcode2017::parse_txtfile(txt_file = .
                                        , sep = "\t"
                                        , map_fun = as.numeric) %>%
        purrr::map(get_even_divisor) %>%
        base::unlist() %>%
        base::sum() %>%
        base::return()
}