[2016-03-21] Challenge #259 [Easy] Clarence the Slow Typist

ctypist.R

#
# [2016-03-21] Challenge #259 [Easy] Clarence the Slow Typist
# https://www.reddit.com/r/dailyprogrammer/comments/4bc3el/20160321_challenge_259_easy_clarence_the_slow/
# Demo at http://www.r-fiddle.org/#/fiddle?id=JwY7VC2k&version=1
#
# Kory Becker 4/3/2016
# http://primaryobjects.com
#

keypad <- data.frame(c(1, 4, 7, 10),
                     c(2, 5, 8, 0),
                     c(3, 6, 9, NA))

getRow <- function(target) {
  # Find the row of the digit within the keypad.
  unlist(sapply(seq(nrow(keypad)), function(rowIndex) {
    row <- keypad[rowIndex,]
    result <- sapply(row, function(digit) {
      target == digit
    })
    if (length(which(result)) > 0) {
      rowIndex
    }
  }))
}

getCol <- function(target) {
  # Find the column of the digit within the keypad.
  unlist(sapply(seq(ncol(keypad)), function(colIndex) {
    col <- keypad[,colIndex]
    result <- sapply(col, function(digit) {
      target == digit
    })
    if (length(which(result)) > 0) {
      colIndex
    }
  }))
}

cost <- function(input) {
  # Remember previous location.
  prev <- c(-1, -1)

  # Calculate all costs for each move along the string.
  parts <- sapply(unlist(strsplit(input, '')), function(digit) {
    # Convert the character into a digit.
    if (digit == '.') {
      digit <- 10
    }
    else {
      digit <- as.numeric(digit)
    }
  
    # Get the (col, row).
    coord <- c(getCol(digit), getRow(digit))
  
    # Calculate distance.
    if (prev[1] == -1) {
      # First time, cost is 0.
      result <- 0
    }
    else if (prev[1] == coord[1] || prev[2] == coord[2]) {
      # Same row or column, cost is the difference in row or col.
      result <- abs(prev[1] - coord[1]) + abs(prev[2] - coord[2])
    }
    else {
      # Diagonal, cost is calculated with pythagoras theorem, where a = row, b = col.
      a <- abs(prev[1] - coord[1])
      b <- abs(prev[2] - coord[2])
      result <- sqrt((a^2) + (b^2))
    }
    
    prev <<- coord
    
    result
  })
  
  sum(parts)
}

format <- function(result) {
  paste0(round(result, 2), 'cm')
}

run <- function(input) {
  format(cost(input))
}

# Challenge input.
run('219.45.143.143')

output.txt

> run('219.45.143.143')
[1] "27.38cm"