Data update

Task/Parsing-RPN-calculator-algorithm/R/parsing-rpn-calculator-algorithm.r

@@ -0,0 +1,36 @@
+rpn <- function(s) {
+  stack <- list()
+  ops <- strsplit(s, " ")[[1]]
+
+  for (op in ops) {
+    if (op %in% c("+", "-", "*", "/", "^")) {
+      arg2 <- stack[[length(stack)]]
+      arg1 <- stack[[length(stack) - 1]]
+      stack <- stack[-c(length(stack), length(stack) - 1)]
+
+      if (op == "+") {
+        res <- as.numeric(arg1) + as.numeric(arg2)
+      } else if (op == "-") {
+        res <- as.numeric(arg1) - as.numeric(arg2)
+      } else if (op == "*") {
+        res <- as.numeric(arg1) * as.numeric(arg2)
+      } else if (op == "/") {
+        res <- as.numeric(arg1) / as.numeric(arg2)
+      } else if (op == "^") {
+        res <- as.numeric(arg1) ^ as.numeric(arg2)
+      }
+
+      stack <- c(stack, res)
+    } else {
+      stack <- c(stack, as.numeric(op))
+    }
+    cat(op, ": ", paste(stack, collapse = ", "), "\n", sep = "")
+  }
+
+  if (length(stack) != 1) {
+    stop(paste("invalid RPN expression:", s))
+  }
+  return(stack[[1]])
+}
+
+rpn("3 4 2 * 1 5 - 2 3 ^ ^ / +")