Implement RPN

src/main.rs

@@ -1,4 +1,4 @@
-use core::fmt;
+use std::collections::HashMap;
 use std::io;
 use std::io::Write;
 
@@ -13,6 +13,7 @@ fn main() {
     stdin.read_line(&mut buffer).unwrap();
 
     let tokens = tokenisator(&buffer);
+    let rpn = to_rpn(tokens);
 
     buffer.clear();
   }
@@ -63,7 +64,49 @@ fn tokenisator(task: &str) -> Vec<Token> {
   return tokens;
 }
 
+fn to_rpn(tokens: Vec<Token>) -> Vec<Token> {
+  let mut out_buf = Vec::<Token>::new();
+  let mut act_buf = Vec::<Token>::new();
+
+  let priority = HashMap::from([
+    (Token::BracketOpen,    0),
+    (Token::Addition,       1),
+    (Token::Substruction,   1),
+    (Token::Multiplication, 2),
+    (Token::Division,       2),
+  ]);
+
+  for t in tokens {
+    match t {
+      Token::Number(_) => out_buf.push(t),
+      Token::BracketOpen => act_buf.push(t),
+      Token::BracketClose => {
+        while matches!(act_buf.last().unwrap(), Token::BracketOpen) {
+          out_buf.push(act_buf.pop().unwrap());
+        }
+        act_buf.pop();
+      }
+      _ => {
+        if !act_buf.is_empty() {
+          while priority.get(&t).unwrap() < priority.get(act_buf.last().unwrap()).unwrap() {
+            out_buf.push(act_buf.pop().unwrap());
+            if act_buf.is_empty() { break; }
+          }
+        }
+
+        act_buf.push(t);
+      }
+    }
+  }
+
+  act_buf.reverse();
+  out_buf.append(&mut act_buf);
+
+  return out_buf;
+}
+
 #[derive(Debug)]
+#[derive(Eq, Hash, PartialEq)]
 enum Token {
   Number(i32),
   Addition,