sgu 123 The sum

题目描述：

123. The sum

time limit per test: 0.5 sec.
memory limit per test: 4096 KB

The Fibonacci sequence of numbers is known: F₁ = 1; F₂ = 1; F_n+1 = F_n + F_n-1, for n>1.You have to find S - the sum of the first K Fibonacci numbers.

Input

First line contains natural number K(0<K<41).

Output

First line should contain number S.

Sample Input

5

Sample Output

12

告诉你K，求前K个Fibonacci数的和。预处理一下或直接暴搞就可以，属于水题。

代码：

#include<iostream>#include<cstring>#include<cstdio>#include<set>#include<algorithm>#include<vector>#include<cstdlib>#define inf 0xfffffff#define CLR(a,b) memset((a),(b),sizeof((a)))using namespace std;int const nMax = 50;typedef long long LL;typedef pair<LL,LL> pij;LL Fi[nMax];LL sum[nMax];int main(){    Fi[0]=0,Fi[1]=1;    for(int i=2;i<nMax;i++)Fi[i]=Fi[i-1]+Fi[i-2];    sum[0]=0;    for(int i=1;i<nMax;i++){        sum[i]=sum[i-1]+Fi[i];    }    int n;    while(cin>>n){        cout<<sum[n]<<endl;    }    return 0;}