poj 2663 Tri Tiling

Tri Tiling

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 5805		Accepted: 3099

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

2
8
12
-1

Sample Output

3
153
2131

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