【考研每日一題19】Fibonacci（C++）

原題地址：牛客網

題目描述：

    The Fibonacci Numbers{0,1,1,2,3,5,8,13,21,34,55...} are defined by the recurrence:     F0=0 F1=1 Fn=Fn-1+Fn-2,n>=2     Write a program to calculate the Fibonacci Numbers.

輸入描述:

    Each case contains a number n and you are expected to calculate Fn.(0<=n<=30) 。

輸出描述:

   For each case, print a number Fn on a separate line,which means the nth Fibonacci Number.

示例1

輸入

1

輸出

1

分析：

斐波那契數列。第三項開始是前兩項的和。

代碼：

#include<iostream>
using namespace std;
int main()
{
    int n;
    int a[31];
    a[0]=0;
    a[1]=1;
    a[2]=1;
    while(cin>>n)
    {
        if(n<=2)cout<<a[n]<<endl;
        else{
            for(int i=3;i<=n;i++)
            {
                a[i]=a[i-2]+a[i-1];
            }
            cout<<a[n]<<endl;
        }
    }
    return 0;
}

2020.4.7