Add Roman Numeral in R

archive/r/r/roman-numeral.R

@@ -0,0 +1,67 @@
+#!/usr/bin/env Rscript
+
+# Function to convert Roman numeral to decimal
+roman_to_decimal <- function(roman) {
+  # Lookup Table of Roman characters against their Hindu-Arabic values
+  values <- c(I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000)
+
+  # Validate that the string contains only valid Roman characters
+  if (!grepl("^[IVXLCDM]*$", roman)) {
+    return(NA)
+  }
+
+  # Split the string into individual characters
+  chars <- strsplit(roman, "")[[1]]
+  numeral_length <- length(chars)
+
+  if (numeral_length == 0) return(0)
+
+  total <- 0
+  i <- 1
+  while (i <= numeral_length) {
+    current_val <- values[chars[i]]
+    next_val <- if (i < numeral_length) values[chars[i + 1]] else 0
+
+    # If current value is less than the next, subtract it (e.g., IV = 4)
+    if (current_val < next_val) {
+      total <- total - current_val
+    } else {
+      total <- total + current_val
+    }
+    i <- i + 1
+  }
+
+  # Basic validation for Roman numeral rules (e.g., preventing "IIII" or "VX")
+  # This checks if converting the result back matches the input
+  # Note: This requires a helper function or a known R function
+  # For strict requirements, we check if the calculated total is valid
+  return(total)
+}
+
+# Capture command line arguments
+args <- commandArgs(trailingOnly = TRUE)
+
+if (length(args) == 0) {
+  cat("Usage: please provide a string of roman numerals\n")
+} else {
+  input <- args[1]
+
+  if (nchar(input) == 0) {
+    cat("0\n")
+  } else {
+    result <- roman_to_decimal(toupper(input))
+
+    if (is.na(result)) {
+      cat("Error: invalid string of roman numerals\n")
+    } else {
+      # Final sanity check: ensure the numeral follows standard additive/subtractive patterns
+      # We use a regex to validate standard Roman Numeral structure
+      valid_pattern <- "^M{0,4}(CM|CD|D?C{0,3})(XC|XL|L?X{0,3})(IX|IV|V?I{0,3})$"
+      if (!grepl(valid_pattern, toupper(input))) {
+        cat("Error: invalid string of roman numerals\n")
+      } else {
+        cat(result, "\n")
+      }
+    }
+  }
+}