day5.r

data <- readLines("data_05.txt")

# find separator line
blank <- which(data == "")

stacks <- data[1:(blank-1)]
instructions <- data[(blank+1):length(data)]

stacks <- strsplit(stacks,"")
rowlen <- length(stacks[[1]])
nst <- length(stacks)
stacks <- unlist(stacks)
stacks <- t(stacks)
stacks <- matrix(stacks,nrow=rowlen, ncol=nst)

rows <- seq(2,rowlen,by=4)
stack_list <- list()

for(i in 1:nst){
  this_row <- stacks[rows[i],]
  this_row <- this_row[!this_row==" "]
  stack_list[[i]]  <- rev(this_row)
}
stack_list2 <- stack_list

# Instructions
get_numbers <- function(x){
  this_inst <- strsplit(x," ")[[1]] 
  this_inst <- as.numeric(this_inst)
  this_inst <- this_inst[!is.na(this_inst)]
  this_inst
}

inst_list <- lapply(instructions,get_numbers)

#
move_crate <- function(crate_list,s_from, s_to){
  the_stack <- crate_list[[s_from]]
  the_crate <- the_stack[length(the_stack)]
  the_stack <- the_stack[-length(the_stack)]
  crate_list[[s_from]] <- the_stack
  crate_list[[s_to]] <- c(crate_list[[s_to]],the_crate)
  crate_list
}

# Move crates
move_crates <- function(crate_list,number,s_from, s_to){
  this_list <- crate_list
  for(i in 1:number){
    this_list <- move_crate(this_list,s_from,s_to)
  }
  return(this_list)
}

for(i in 1:length(instructions)){
  stack_list <- move_crates(stack_list,inst_list[[i]][1],inst_list[[i]][2],inst_list[[i]][3])
}

for(i in stack_list){
  cat(i[length(i)])
}


# part 2

# Move crates
stack_list <- stack_list2

move_crates <- function(this_stack,number,s_from, s_to){
  from_stack <- this_stack[s_from][[1]]
  to_stack <- this_stack[s_to][[1]]
  crates <- from_stack[(length(from_stack)-(number-1)):length(from_stack)]
  from_stack <- from_stack[1:(length(from_stack)-(number))]
  to_stack <- c(to_stack,crates)
  this_stack[[s_from]] <- from_stack
  this_stack[[s_to]] <- to_stack
  return(this_stack)
}

for(i in 1:length(instructions)){
  stack_list <- move_crates(stack_list,inst_list[[i]][1],inst_list[[i]][2],inst_list[[i]][3])
}

for(i in stack_list){
  cat(i[length(i)])
}