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Task/Penneys-game/R/penneys-game.r

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+#===============================================================
+# Penney's Game Task from Rosetta Code Wiki
+# R implementation
+#===============================================================
+
+penneysgame <- function() {
+
+  #---------------------------------------------------------------
+  # Who goes first?
+  #---------------------------------------------------------------
+
+  first <- sample(c("PC", "Human"), 1)
+
+  #---------------------------------------------------------------
+  # Determine the sequences
+  #---------------------------------------------------------------
+
+  if (first == "PC") { # PC goes first
+
+    pc.seq <- sample(c("H", "T"), 3, replace = TRUE)
+    cat(paste("\nI choose first and will win on first seeing", paste(pc.seq, collapse = ""), "in the list of tosses.\n\n"))
+    human.seq <- readline("What sequence of three Heads/Tails will you win with: ")
+    human.seq <- unlist(strsplit(human.seq, ""))
+
+  } else if (first == "Human") { # Player goest first
+
+    cat(paste("\nYou can choose your winning sequence first.\n\n"))
+    human.seq <- readline("What sequence of three Heads/Tails will you win with: ")
+    human.seq <- unlist(strsplit(human.seq, "")) # Split the string into characters
+    pc.seq <- c(human.seq[2], human.seq[1:2]) # Append second element at the start
+    pc.seq[1] <- ifelse(pc.seq[1] == "H", "T", "H") # Switch first element to get the optimal guess
+    cat(paste("\nI win on first seeing", paste(pc.seq, collapse = ""), "in the list of tosses.\n"))
+
+  }
+
+  #---------------------------------------------------------------
+  # Start throwing the coin
+  #---------------------------------------------------------------
+
+  cat("\nThrowing:\n")
+
+  ran.seq <- NULL
+
+  while(TRUE) {
+
+    ran.seq <- c(ran.seq, sample(c("H", "T"), 1)) # Add a new coin throw to the vector of throws
+
+    cat("\n", paste(ran.seq, sep = "", collapse = "")) # Print the sequence thrown so far
+
+    if (length(ran.seq) >= 3 && all(tail(ran.seq, 3) == pc.seq)) {
+      cat("\n\nI win!\n")
+      break
+    }
+
+    if (length(ran.seq) >= 3 && all(tail(ran.seq, 3) == human.seq)) {
+      cat("\n\nYou win!\n")
+      break
+    }
+
+    Sys.sleep(0.5) # Pause for 0.5 seconds
+
+  }
+}