150. Evaluate Reverse Polish Notation

150. Evaluate Reverse Polish Notation/150. Evaluate Reverse Polish Notation.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>net8.0</TargetFramework>
+        <RootNamespace>_150._Evaluate_Reverse_Polish_Notation</RootNamespace>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+    </PropertyGroup>
+
+</Project>

150. Evaluate Reverse Polish Notation/Program.cs

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+// See https://aka.ms/new-console-template for more information
+
+using _150._Evaluate_Reverse_Polish_Notation;
+
+string[] arr = ["10", "1", "1", "2", "+", "+", "+"];
+var sol = new Solution();
+int n = 100000;
+while(n-- > 0)
+    Console.WriteLine(sol.EvalRPN(["10", "1", "1", "2", "+", "+", "+"]));
+
+    

150. Evaluate Reverse Polish Notation/Solution.cs

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+namespace _150._Evaluate_Reverse_Polish_Notation;
+
+public class Solution
+{
+    public int EvalRPN(string[] tokens)
+    {
+        var stack = new Stack<int>(tokens.Length);
+        foreach (var token in tokens)
+        {
+            if (int.TryParse(token, out var number))
+                stack.Push(number);
+            else
+            {
+                int right = stack.Pop();
+                int left = stack.Pop();
+                char op = token[0];
+                stack.Push(Calc(op, left, right));
+            }
+        }
+        return stack.Pop();
+    }
+
+    private int Calc(char op, int left, int right) => op switch
+    {
+        '+' => left + right,
+        '-' => left - right,
+        '*' => left * right,
+        '/' => left / right,
+        _ => throw new ArgumentOutOfRangeException()
+    };
+}