day2.r

# Data file is as provided
data <- read.delim("data_02.txt",header=FALSE,sep=" ")

# Simple lsit to look up scores for Rock/Paper/Scissors
scores <- list(X=1, Y=2, Z=3)

# Look-up matrix for win/lose/draw conditions, R/P/S in rows/columns
WLD <- matrix(c(3,0,6,
                6,3,0,
                0,6,3),nrow=3)

# Look up vectors, just to convert letters to 1,2,3 array indices
vec_home <- c("A","B","C")
vec_away <- c("X","Y","Z")

# For given home (A/B/C) and away (X/Y/Z) return total score for round
game_score <- function(home,away){
  home_idx <- which(vec_home == home) # get numeric index
  away_idx <- which(vec_away == away) # get numeric index
  m_score <-WLD[home_idx,away_idx] # use indices to look up score
  m_score + scores[[away]] # add score to hand score
}

# Function to process each line of file through game_score function
process_round <- function(x){
  this_round <- data[x,]
  game_score(this_round$V1,this_round$V2)
}

# Map file through process_round function then sum - I prefer purrr, i've forgotten the
# efficient way to do this in base!
final_score <- sum(unlist(lapply(1:nrow(data),process_round)))
print(final_score)

# Part 2- look-up matrix for given A/B/C, X/Y/Z inputs, what hand do I need to
# meet the plan?
NEW_WLD <- matrix(c("Z","X","Y",
                    "X","Y","Z",
                    "Y","Z","X"),nrow=3)

# Function to use the NEW_WLD matrix to tell me what hand I need
get_correct <- function(home,away){
  home_idx <- which(vec_home == home)
  away_idx <- which(vec_away == away)
  NEW_WLD[home_idx,away_idx]
}

# Process as before, but look up the hand I need and use it instead
process_round2 <- function(x){
  this_round <- data[x,]
  which_hand <- get_correct(this_round$V1,this_round$V2)
  game_score(this_round$V1,which_hand)
}

# Apply
final_score <- sum(unlist(lapply(1:nrow(data),process_round2)))
print(final_score)