[백준] 2747번: 피보나치 수 [C#]

 

using System.IO;
using System.Text;
using System.Linq;
using System.Reflection.PortableExecutable;
using System.Security.Cryptography;
 
namespace 연습장
{
    internal class Program
    {
        static StringBuilder sb = new StringBuilder();
        static void Main(string[] args)
        {
            using var reader = new StreamReader(Console.OpenStandardInput());
            using var print = new StreamWriter(Console.OpenStandardOutput());
 
            _2747_boj boj = new _2747_boj();
 
            boj.boj_2747();
 
        }
    }
        internal class _2747_boj
    {
        public void boj_2747()
        {
            int n = int.Parse(Console.ReadLine());
 
            long[] dp = new long[n + 1];
            dp[0] = 0;
            if (n >= 1)
                dp[1] = 1;
            if (n >= 2)
                dp[2] = 1;
            if (n <= 2){
                Console.WriteLine(dp[n]);
                return;
            }
 
            for (int i = 3; i <= n; i++)
            {
                dp[i] = dp[i - 2] + dp[i - 1];
            }
            Console.WriteLine(dp[n]);
        }
    }
}