Solving Advent of Code 2020-08 with R.
[Disclaimer] Obviously, this post contains a big spoiler about Advent of Code.
Instructions
Input looks like this
nop +0
acc +1
jmp +4
acc +3
jmp -3
acc -99
acc +1
jmp -4
acc +6
There is a global var called
accumulator, starting at 0acc nincreases or decreasesaccumulatorbyn, and goes to next rowjmp njumps to a its position +nnopdoes nothing but going to the next executionIf the program tries to execute a row twice, we stop, and the eturned value is the value just before that
Find the complete instructions at:https://adventofcode.com/2020/day/8.
R solution
Part one
# Reading the data
input <- read.delim(
sep = " ",
"2020-08-aoc.txt",
header = FALSE,
stringsAsFactors = FALSE
)
give_me_a_break <- function(input){
accumultor <- 0
current_row <- 1
done_row <- c()
exit_code <- 0
while(TRUE){
if (current_row %in% done_row){
exit_code <- 1
break
}
if (current_row > nrow(input)){
break
}
done_row <- c(done_row, current_row)
curr_row <- input[current_row,]
if (curr_row$V1 == "nop") {
current_row <- current_row + 1
}
if (curr_row$V1 == "acc") {
accumultor <- accumultor + curr_row$V2
current_row <- current_row + 1
}
if (curr_row$V1 == "jmp") {
current_row <- current_row + curr_row$V2
}
}
return(
list(
accumultor = accumultor,
exit_code = exit_code
)
)
}
give_me_a_break(input)
## $accumultor
## [1] 1528
##
## $exit_code
## [1] 1
Part two
for (i in which(input$V1 %in% c("nop", "jmp"))){
modified_ipt <- input
if (modified_ipt[i, 'V1'] == "nop"){
modified_ipt[i, 'V1'] <- "jmp"
} else {
modified_ipt[i, 'V1'] <- "nop"
}
res <- give_me_a_break(modified_ipt)
if (res$exit_code == 0){
print(res$accumultor)
break
}
}
## [1] 640
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