poj 2663 Tri Tiling 状压dp

#include <iostream>
using namespace std;
__int64 ans[32][4];
int n,m;
__int64 dp[2][1<<4];

__int64 solve()
{
	int i,j,used;
	memset(dp,0,sizeof(dp));
	__int64 *crt=dp[0],*nxt=dp[1];
	crt[0]=1;
	for(i=n-1;i>=0;--i)
		for(j=m-1;j>=0;--j){
			for(used=0;used<(1<<m);++used){
				if(used>>j&1)
					nxt[used]=crt[used&(~(1<<j))];		
				else{
					__int64 res=0;
					if(j+1<m&&!(used>>(j+1)&1))
						res+=crt[used|1<<(j+1)];
					if(i+1<n)
						res+=crt[used|(1<<j)];
					nxt[used]=res;
				}
			}
			swap(crt,nxt);
		}
	return crt[0];
}

int main()
{
	while(scanf("%d",&n)==1){
		if(n==-1)
			break;
		m=3; 
		memset(ans,-1,sizeof(ans));
		if(n<m)
			swap(n,m);			
		if(ans
[m]!=-1){
			printf("%I64d\n",ans
[m]);
			continue;
		}
		if((n*m)%2==1)
			ans
[m]=0;
		else
			ans
[m]=solve();
		printf("%I64d\n",ans
[m]);
	}
	return 0;	
}