C # is implemented by a recursive algorithm: the rules for a number of columns are as follows: 1, 1, 2, 3, 5, 8, 13, 21, 34, how much is the 30th digit _c# tutorial

Method One: Recursive algorithm

<summary>
///The rules for a number of columns are as follows: 1, 1, 2, 3, 5, 8, 13, 21, 34 to find the number of 30th digits, with a recursive algorithm to achieve. (C # language)
</summary>
///<param name= "pos" ></param>
///<returns></returns>
public int Getnumberatpos (int pos)
{
  if (pos==0| | Pos==1)
  {return
    1;
  }
  int res = Getnumberatpos (pos-1) + Getnumberatpos (pos-2);
  return res;
}

Method Two: Do not have recursion

Using System;
Using System.Collections;
Using System.Collections.Generic;

Using System.Text;

    Namespace Test {public class Class1 {private ArrayList list = new ArrayList ();

      Public Class1 () {} public Class1 (int num): base () {int i; for (i = 1; I <= num; i++) {list.
      ADD (calculation (i));
      } private int calculation (int num) {if (num = 1 | | num = 2) return 1;
    else return Convert.ToInt32 (list[num-2]) + Convert.ToInt32 (list[num-3)); public int calculation () {return Convert.ToInt32 (list[list).
    Count-1]);
      The public class Test {public static void Main () {int J;
      int num;
        for (j = 1; J < + j) {Console.WriteLine ("How many digits do you want to count:");
        String Readstr;
        Readstr = Console.ReadLine (); if (!string. IsNullOrEmpty (READSTR)) {if (int).
     TryParse (readstr, out num))     {if (num < 1) continue;
              else {Class1 C1 = new Class1 (num); Console.WriteLine (C1.
            Calculation ());
          } else {continue;
        } else {break;

 }
      }
    }
  }
}

Method Three: Use the loop to realize

public long getnumber (int pos)
{
  long one = 1;
  Long two = 1;
  if (pos = 0 | | | pos = 1)
  {return
    1;
  }
  int i = 3;
  Long sum = 1;
  while (I <= Pos)
  {
    sum = one + two;
    one = two;
    two = sum;
    i++;
  }
  return sum;
}

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