ural 1225 Flags



1225. Flags

Time limit: 1.0 second

Memory limit: 64 MB

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:

Input

N, the number of the stripes, 1 ≤ N ≤ 45.

Output

M, the number of the ways to decorate the shop-window.

Sample

input	output
3	4

Problem Source: 2002-2003 ACM Central Region of Russia Quarterfinal Programming Contest, Rybinsk, October 2002

Tags: dynamic programming  (

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题意：蓝色只能在白红之间，不能连续放同一个颜色。问有几种方法
水题，简单DP。

#include <algorithm>
#include <map>
#include <cstring>
#include <cmath>
#include <iostream>
using namespace std;
#define lson l , m , rt << 1
#define rson m + 1 , r , rt << 1 | 1
#define LL __int64
typedef long long ll;
#define PI 3.1415926
ll dp[46];
int main()
{
int i;
dp[1]=2;
dp[2]=2;
dp[3]=4;
for(i=4;i<=45;i++)
dp[i]=dp[i-1]+dp[i-2];
int n;
while(cin>>n)
cout<<dp
<<endl;
return 0;
}