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- library(stringr)
- input <- readLines("input5.txt")
- im <- str_match(input, "^([BF])([BF])([BF])([BF])([BF])([BF])([BF])([RL])([RL])([RL])$")
-
- rowspec <- apply(im[,2:8], c(1,2), function(x) {x == "B"})
- colspec <- apply(im[,9:11], c(1,2), function(x) {x == "R"})
- rownums <- as.vector(rowspec%*%(2^((ncol(rowspec)-1):0)))
- colnums <- as.vector(colspec%*%(2^((ncol(colspec)-1):0)))
- id <- rownums * 8 + colnums
-
- # Part a
- max(id)
-
- # Part b
- idl <- sort(id)
- idl[which.max(diff(idl))] + 1
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