Fibonacci数列的多种求法

int Fibonacci(int n)
{
  int a = 0, b = 1;
  while (n--)
  {
    b = a + b;
    a = b - a;
  }
  return a;
 }
int Fibonacci(int n)
{
  if (n <= 0)
    return 0;
  if (n==1||n==2)
    return 1;
    return Fibonacci(n - 1) + Fibonacci(n - 2);
}
int Fibonacci(int n)
{
  int a[100] = { 0 };
  a[1] = 1;
  a[2] = 1;
  for (int i = 3; i <= n; i++)
    a[i] = a[i - 1] + a[i - 2];
  return a[n];
}