poj 2663

 

Tri Tiling

Time Limit: 1000MS Memory Limit: 65536KTotal Submissions: 5361 Accepted: 2853

Description

In how many ways can you tile a 3xn rectangle with 2x1 dominoes? 
Here is a sample tiling of a 3x12 rectangle. 

Input

Input consists of several test cases followed by a line containing -1. Each test case is a line containing an integer 0 <= n <= 30.

Output

For each test case, output one integer number giving the number of possible tilings.

Sample Input

2812-1

Sample Output

31532131

Source

Waterloo local 2005.09.24

分析：其实本是道水题的，我居然。。。while(scanf("%d",&n),n>0)wa了无数次‍

。。。：

#include<cstdio>int i=4,n,a[31]={0};int main(){ for(a[0]=1,a[2]=3;i<31;++i)a[i]=a[i-2]*4-a[i-4]; while(scanf("%d",&n),n>-1)printf("%d/n",a[n]); return 0;}