Question

c++ 用数组求Fibonacci数列的第N项和前N项和

#include<iostream>
#include<cmath>
using namespace std;

int main()
{
int i,sum,n;
cout<<"please enter the number : "<<endl;
cin>>n;
int F[50]; /*计算第n项*/
F[0]=0;
F[1]=1;
if(n>=2)
i=n;
for(i=2;i<n;i++)
{F[i]=F[i-1]+F[i-2];}
if(n==0) /*计算前n项和*/
sum=0;
if(n==1)
sum=1;
for(i=0;i<n;i++)
{sum+=F[i];}
cout<<"the number in Fibonacci is : "<<F[n]<<endl;
cout<<"the sum is : "<<sum<<endl;
return 0;
}

请问错哪了啊？怎么改？

Answer 1

#include<iostream>
#include<cmath>
using namespace std;

int main()
{
int i,sum,n;
cout<<"please enter the number : "<<endl;
cin>>n;
int F[50]; /*计算第n项*/
F[0]=0;
F[1]=1;
// if(n>=2)
// i=n;
for(i=2;i<=n;i++) //
{F[i]=F[i-1]+F[i-2];}
// if(n==0) /*计算前n项和*/
sum=0;
// if(n==1)
// sum=1;
for(i=0;i<=n;i++) //
{sum+=F[i];}
cout<<"the number in Fibonacci is : \n"; //<<F[n]<<endl;
for(i=0;i<=n;i++) //
cout <<F[i] <<" "; //
cout <<endl; //
cout<<"the sum is : "<<sum<<endl;
return 0;
}

Answer 2

sum需要赋初值=0;