nyoj 461

题目来源：http://acm.nyist.net/JudgeOnline/problem.php?pid=461

#include <iostream>#include <cstdio>#include <cstring>#include <cmath>using namespace std;//f(n)=n*log10((1+sqrt(5))/2)-log10(sqrt(5))int main(){    int arr[22];    arr[0] = 0, arr[1] = 1;    for(int i = 2; i <= 20; ++i)        arr[i] = arr[i-1] + arr[i-2];    int n, res, ans2;    double ans1, ans3;    while(~scanf("%d", &n))    {        if(n <= 20)        {            printf("%d\n", arr[n]);            continue ;        }        ans1 = n*log10(0.5+0.5*sqrt(5))-log10(sqrt(5));        ans2 = (int)ans1;        ans1 -= ans2;        ans3 = pow(10.0, ans1);        res = ans3*1000;        printf("%d\n", res);    }    return 0;}