Fibonacci Sequence(斐波那契数列递归)

1、question:find The nth number offibonacci sequence

    In mathematics, the Fibonaccinumbers are the numbers in the following integer sequence, calledthe Fibonacci         sequence, and characterized by the fact that everynumber after the first two is the sum of the two preceding ones:

     1 1 2 3 5 8 13 21 34 55 89 144.....

2、code:

#include<iostream>
#include<cstdio>
using namespace std;
int fib(int a)
{
if(a==0) return 0;
if(a==1) return 1;
else
{
return fib(a-1)+fib(a-2);
}
}
int n;
int main()
{
cin>>n;
cout<<fib(n);
return 0;

}

3、running