自部落格園轉載：

1.遞迴

效率低，除了最後一個數，每個數都被重複計算若干次

1: //遞迴實現
   2: public static int Fib1(int n)
   3: {
   4:     if (n < 3)
   5:     {
   6:         return 1;
   7:     }
   8:     else
   9:     {
  10:         return Fib1(n - 1) + Fib1(n - 2);
  11:     }
  12: }

2.迭代

效率最高，時間複雜度O(n)，空間複雜度是O(1)

1: //迭代實現
   2: public static int Fib2(int n)
   3: {
   4:     if (n < 3)
   5:     {
   6:         return 1;
   7:     }
   8:     else
   9:     {
  10:         int first = 1;
  11:         int second = 1;
  12:         int temp = 0;
  13:  
  14:         for (int i = 0; i < n - 2; i++)
  15:         {
  16:             temp = first + second;
  17:             first = second;
  18:             second = temp;
  19:         }
  20:         return temp;
  21:     }
  22: }
 

3.陣列

效率一般，比遞迴快，時間複雜度O(n)，空間複雜度是O(n)

 1: //陣列實現
   2: public static int Fib3(int n)
   3: {
   4:     List<int> list = new List<int>();
   5:     list.Add(1);
   6:     list.Add(1);
   7:     int count = list.Count;
   8:  
   9:     while (count < n)
  10:     {
  11:         list.Add(list[count - 2] + list[count - 1]);
  12:         count = list.Count;
  13:     }
  14:  
  15:     return list[count - 1];
  16: }
 

4.佇列

時間複雜度O(n)，空間複雜度是O(1)

1: //佇列實現
   2: public static int Fib4(int n)
   3: {
   4:     Queue<int> queue = new Queue<int>();
   5:     queue.Enqueue(1);
   6:     queue.Enqueue(1);
   7:  
   8:     for (int i = 0; i <= n - 2; i++)
   9:     {
  10:         queue.Enqueue(queue.AsQueryable().First() + queue.AsQueryable().Last());
  11:         queue.Dequeue();
  12:     }
  13:     return queue.Peek();
  14: }