Data update

Task/Move-to-front-algorithm/R/move-to-front-algorithm.r

@@ -0,0 +1,28 @@
+encodeMTF <- function(str, symtable = letters) {
+  encode <- function(ch) {
+    r <- which(symtable == ch)
+    symtable <<- c(ch, symtable[-r])
+    return(r)
+  }
+  sapply(strsplit(str, "")[[1]], encode)
+}
+
+decodeMTF <- function(arr, symtable = letters) {
+  decode <- function(i) {
+    r <- symtable[i]
+    symtable <<- c(r, symtable[-i])
+    return(r)
+  }
+  paste(sapply(arr, decode), collapse = "")
+}
+
+testset <- c("broood", "bananaaa", "hiphophiphop")
+encoded <- lapply(testset, encodeMTF)
+decoded <- mapply(decodeMTF, encoded)
+
+for (i in seq_along(testset)) {
+  cat("Test string:", testset[i], "\n -> Encoded:", paste(encoded[[i]], collapse = ", "), "\n -> Decoded:", decoded[i], "\n\n")
+}
+
+# Test if decoded strings equal original
+all(sapply(seq_along(testset), function(i) identical(testset[i], decoded[i])))