add day 10

Author: rrrlw

2021/day10.R

@@ -0,0 +1,98 @@
+#####SETUP#####
+library(magrittr)
+library(dequer)
+
+#####INPUT#####
+fin <- file("day10.in", open = "r")
+vals <- readLines(fin) %>%
+  strsplit(split = "", fixed = TRUE)
+close(fin)
+
+#####UTILITY#####
+OPEN <- c("(", "[", "{", "<")
+CLOSE<- c(")", "]", "}", ">")
+names(OPEN) <- CLOSE
+names(CLOSE) <- OPEN
+first_mistake <- function(line) {
+  s <- stack()
+  
+  for (i in line) {
+    
+    if (i %in% OPEN) push(s, i)
+    
+    else if (i %in% CLOSE) {
+      
+      last <- pop(s)
+      if (OPEN[i] != last) return(i)
+      
+    } else {
+      stop(paste("UNEXPECTED CHAR:", i))
+    }
+  }
+  
+  return(" ")
+}
+
+complete_str <- function(line) {
+  s <- stack()
+  
+  for (i in line) {
+    
+    if (i %in% OPEN) push(s, i)
+    else if (i %in% CLOSE) pop(s)
+    
+  }
+  
+  ans <- ""
+  while (length(s) > 0) {
+    ans <- paste0(ans, CLOSE[pop(s)])
+  }
+  
+  return(ans)
+}
+
+VALS1 <- c(")" = 3, "]" = 57, "}" = 1197, ">" = 25137, " " = 0)
+get_points1 <- function(chr) {
+  vapply(
+    X = chr,
+    USE.NAMES = FALSE,
+    FUN.VALUE = numeric(1),
+    FUN = function(curr) {
+      VALS1[curr]
+    }
+  )
+}
+
+VALS2 <- c(")" = 1, "]" = 2, "}" = 3, ">" = 4)
+get_points2 <- function(chr) {
+  chr <- chr %>%
+    strsplit(split = "", fixed = TRUE) %>%
+    unlist
+  
+  counter <- 0
+  
+  for (i in chr) {
+    counter <- counter * 5 + VALS2[i]
+  }
+  
+  return(counter)
+}
+
+#####PART 1#####
+vals %>%
+  lapply(FUN = first_mistake) %>%
+  lapply(FUN = get_points1) %>%
+  unlist %>%
+  sum
+
+#####PART 2#####
+incomplete <- lapply(X = vals, FUN = first_mistake) %>%
+  unlist %>%
+  equals(" ") %>%
+  which
+
+vals[incomplete] %>%
+  lapply(FUN = complete_str) %>%
+  lapply(FUN = get_points2) %>%
+  unlist %>%
+  median