hdu 1143 Tri Tiling

Tri Tiling

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 2125    Accepted Submission(s): 1215

Problem 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

 

#include <iostream>using namespace std;int main(){    int f[31]={0};    f[0]=1;    f[2]=3;    for (int i=4; i<31; i+=2)    {        f[i]=4*f[i-2]-f[i-4];    }    int n;    while (cin>>n  && n>=0)    {        cout<<f[n]<<endl;    }    return 0;}