Add 509. Fibonacci Number recursive solution

Author: Rion5

LeetCode/FibonacciNumber.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace LeetCodeSolutionsLib
+{
+ /// <summary>
+ /// 509. Fibonacci Number
+ /// The Fibonacci numbers, commonly denoted to F(n) form a sequence, called the Fibonacci sequence, such that each number is the sum of two preceeding ones, start from 0 and 1.
+ /// IE) Input : [4]
+ /// Output : [3]
+ /// Explanation: F(4) = F(3) + F(2) ==> 2 + 1 = 3
+ /// </summary>
+ public class FibonacciNumber : Solution
+ {
+ private int n;
+
+ public FibonacciNumber(int n)
+ {
+ this.n = n;
+ }
+
+ private int fib(int n)
+ {
+ // Base cases
+ int result = 0;
+ if (n == 0) return result;
+ if (n == 1 || n == 2)
+ {
+ result = 1;
+ }
+ // Otherwise use recursion to calculate the Fibonacci Number
+ else
+ {
+ result = fib(n - 1) + fib(n - 2);
+ }
+ return result;
+ }
+
+ public override void PrintExample()
+ {
+ var watch = System.Diagnostics.Stopwatch.StartNew();
+ var results = fib(this.n);
+ watch.Stop();
+ Console.WriteLine($"509. Fibonacci Number\n" +
+ $"Input Num = {this.n} \n" +
+ $"Result: [{results}] \n" +
+ $"Execution Speed: {watch.ElapsedMilliseconds}ms \n");
+ }
+ }
+}

LeetCodeConsoleApp/Program.cs

@@ -152,6 +152,13 @@ static void Main(string[] args)
 
  #endregion
 
+ #region 509. Fibonacci Number
+
+ FibonacciNumber fibonacciNumber = new FibonacciNumber(10);
+ fibonacciNumber.PrintExample();
+
+ #endregion
+
  #region 622. MyCircularQueue
 
  MyCircularQueue myCircularQueue = new MyCircularQueue(1);