Top Student

Part of the Logic & Flow section of Coddy's R journey. Lesson 26 of 64.

Challenge

Medium

Add the TOP command. Keep every command from the previous steps working exactly as before.

TOP: reply Top: followed by the student with the highest mean and that mean with one decimal in brackets, such as Top: ada (92.0). Students without grades are skipped. When means tie, pick the student whose name comes first alphabetically. When no student has grades, reply Top: none.

The supplied code passes every input line to gradebook() as one command and prints each returned reply on its own line. A name is one lower-case word, and the input holds only the commands described so far.

Try it yourself

average_text <- function(scores) {
  if (length(scores) == 0) "no grades" else sprintf("%.1f", mean(scores))
}

gradebook <- function(commands) {
  grades <- list()
  replies <- c()
  for (cmd in commands) {
    parts <- strsplit(cmd, " ")[[1]]
    name <- parts[2]
    if (parts[1] == "ADD") {
      if (name %in% names(grades)) {
        replies <- c(replies, paste(name, "already exists"))
      } else {
        grades[[name]] <- numeric(0)
        replies <- c(replies, paste("added", name))
      }
    } else if (parts[1] == "GRADE") {
      if (!(name %in% names(grades))) {
        replies <- c(replies, paste("no student", name))
      } else {
        score <- as.numeric(parts[3])
        grades[[name]] <- c(grades[[name]], score)
        replies <- c(replies, paste("recorded", score, "for", name))
      }
    } else if (parts[1] == "AVG") {
      if (!(name %in% names(grades))) {
        replies <- c(replies, paste("no student", name))
      } else {
        replies <- c(replies, paste0(name, ": ", average_text(grades[[name]])))
      }
    } else if (parts[1] == "REPORT") {
      for (student in sort(names(grades))) {
        replies <- c(replies, paste0(student, ": ", average_text(grades[[student]])))
      }
      replies <- c(replies, paste("Class average:", average_text(unlist(grades))))
    }
  }
  replies
}

# Supplied input/output code: keep it as it is
input <- suppressWarnings(readLines(file("stdin")))
cat(gradebook(input), sep = "\n")