Advent of Code 2021 in R - Day 1

AdventOfCode2021_d01_main.R

# ------------------------------------------------------------------------------------------
# Solution with Reduce
# Challenge 1
find_increase <- function(accumulated, next_val) {
  is_increase = !is.na(accumulated$previous) && accumulated$previous < next_val
  list(
    previous = next_val,
    count = accumulated$count + ifelse(is_increase, 1, 0)
    )
}

readr::read_lines("./days/d01/data.txt") %>%
  as.integer() %>%
  purrr::reduce(find_increase,
                .init = list(previous=NA_integer_, count=0))
  
# Challenge 2
readr::read_lines("./days/d01/data.txt") %>%
  as.integer() %>%
  slider::slide(~sum(.x), .after = 2) %>%
  purrr::reduce(find_increase,
                .init = list(previous=NA_integer_, count=0))

# ------------------------------------------------------------------------------------------
# Solution with Partition 
# Challenge 1

partition <- function(x, n) {
  r <- embed(x, n)[, n:1]
  split(r, row(r))
}
# Or
# partition <- \(x,n) Map(\(i) x[i:(i+n)], seq(length(x)-n))

readr::read_lines("./days/d01/data.txt") %>%
  as.integer() %>%
  partition(2) %>% 
  purrr::keep(~ .[2] > .[1]) %>% 
  length()

# Challenge 2
readr::read_lines("./days/d01/data.txt") %>%
  as.integer() %>%
  partition(3) %>% 
  partition(2) %>% 
  purrr::map_depth(2, sum) %>% 
  purrr::keep(~ .[[2]] > .[[1]]) %>% 
  length()