Day10

509. Fibonacci Number/509. Fibonacci Number.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_509._Fibonacci_Number</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

509. Fibonacci Number/Program.cs

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+namespace _509._Fibonacci_Number;
+
+internal class Program
+{
+    static void Main(string[] args)
+    {
+    }
+}

509. Fibonacci Number/Solution.cs

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+namespace _509._Fibonacci_Number;
+
+public class Solution
+{
+    public int Fib(int n)
+    {
+        if (n == 0)
+            return 0;
+        n--;
+        int cur0 = 0;
+        int cur1 = 1;
+        while (--n > 0)
+        {
+            int buf = cur0 + cur1;
+            cur0 = cur1;
+            cur1 = buf;
+        }
+        return cur0 + cur1;
+    }
+}