Flags
Time Limit:1000MS Memory Limit:65536KB 64bit IO Format:%I64d & %I64u
Submit Status
Description
On the Day of the Flag of Russia a shop-owner decided to decorate the show-window of his shop with textile stripes of white, blue and red colors. He wants to satisfy the following conditions:
Stripes of the same color cannot be placed next to each other.
A blue stripe must always be placed between a white and a red or between a red and a white one.
Determine the number of the ways to fulfill his wish.
Example. For N = 3 result is following:
Problem illustration
Input
N, the number of the stripes, 1 ≤ N ≤ 45.
Output
M, the number of the ways to decorate the shop-window.
Sample Input
input output
3
4
放第i个的时候，有两种方法：
一、在第i 个上放上与i-1个相反的颜色（第i-1个是红色，则放白色，否则放红色）;
二、将第i-1个的颜色改成蓝色的;
综合上述的两种情况：ans[i]=ans[i-1]+ans[i-2]
/*************************************************************************
> File Name: h.cpp
> Author:yuan
> Mail:
> Created Time: 2014年11月09日 星期日 20时41分18秒
************************************************************************/
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cstdlib>
#include<cmath>
using namespace std;
long long ans[50];
int n;
int main()
{
ans[1]=ans[2]=2;ans[0]=0;
for(int i=3;i<=45;i++)
{
ans[i]=ans[i-1]+ans[i-2];
}
while(~scanf("%d",&n)){
printf("%I64d
",ans[n]);
}
return 0;
}