HDU 1143

Tri Tiling

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 2764    Accepted Submission(s): 1559

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<stdio.h>using namespace std;int n;long long dp[32];int main(){    dp[0] = 1;    dp[2] = 3;    dp[4] = 11;    for(int i = 6; i < 32; i+=2)        dp[i] = 3*dp[i-2] + dp[i-2] - dp[i-4];    while(~scanf("%d",&n))    {        if(-1 == n)            break;        printf("%lld\n",dp[n]);    }    return 0;}