From 51d955fbdada4400c8efd504d637b4ece6fcee22 Mon Sep 17 00:00:00 2001
From: Stoycho Kyosev <stoycho.kk@gmail.com>
Date: Wed, 12 Oct 2022 15:42:41 +0300
Subject: add seminar02

---
 Seminar02/task03.cpp | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 Seminar02/task03.cpp

(limited to 'Seminar02/task03.cpp')

diff --git a/Seminar02/task03.cpp b/Seminar02/task03.cpp
new file mode 100644
index 0000000..d460551
--- /dev/null
+++ b/Seminar02/task03.cpp
@@ -0,0 +1,59 @@
+#include<iostream>
+#include<stack>
+#include<string>
+#include<cassert>
+
+bool isOperation(char c) {
+    return (c == '+') || (c == '-') || (c == '*') || (c == '/');
+}
+
+bool isDigit(char c) {
+    return c >= '0' && c <= '9';
+}
+
+int eval(int fst, int snd, char op) {
+    assert(isOperation(c));
+    
+    switch (op) {
+    case '+':
+        return fst + snd;  
+    case '-':
+        return fst - snd;
+    case '*':
+        return fst * snd;
+    case '/':
+        return fst / snd;
+    }
+}
+
+int RPN(const std::string& str) {
+    std::stack<int> numbers;
+
+    for (size_t i = 0; i < str.size(); i++) {
+        if(isOperation(str[i])) {
+            int snd = numbers.top();
+            numbers.pop();
+
+            int fst = numbers.top();
+            numbers.pop();
+
+            numbers.push(eval(fst, snd, str[i]));
+        }
+        else if(str[i] != ' ') {
+            int number = 0;
+            while(i < str.size() && isDigit(str[i])) {
+                number *= 10;
+                number += str[i] - '0';
+                i++;
+            }
+            i--;
+            numbers.push(number);
+        }
+    }
+    
+    return numbers.top();
+}
+
+int main() {
+    std::cout << RPN("9 3 4 * - 2 5 * -");
+}
\ No newline at end of file
-- 
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