HDU1143Tri Tiling

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Tri Tiling

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 1755 Accepted Submission(s): 996

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

这个题目看了别人的递归公式：a[i] = a[i-1] * 4 - a[i-2]; a[0]=1;a[2]=3; n为奇数时，为0；

AC code：

#include <iostream>using namespace std;int main(){__int64 a[35],n,i;memset(a,0,sizeof(a));a[0]=1;a[2]=3;for(i=4; i<=30; i+=2)a[i]=4*a[i-2]-a[i-4];while(~scanf("%I64d",&n)){if(n==-1)break;   printf("%I64d\n",a[n]);}return 0;}

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