<div class="post_brief"><p>
插头dp的练手题么。虽然之前还没写过哈密顿回路的题。</p>

 

学习了一下广义括号法。发现状态数比之前记连通性的方法要少。仔细想想发现，两个连通的插头的顺序有关。不能存在1212这种东西。所以连通性的方法记了很多废状态。那把连通性方法改进一下会不会变得更快呢？可以研究一下。我觉得应该是等效了吧。

 

今天的debug时间明显缩短了。虽然还是debug了老半天。然后怎么代码还是那么长。想起我每次都觉得把东西挤到一起看起来很不雅观，于是去写一堆找转移的函数。晕。

 

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;


typedef long long dint;
#ifdef WIN32
#define lld “%I64d”
#else
#define lld “%lld”
#endif
#define _l (long long int)


const int maxn = 15;
const int maxst = 50009;


#define mbit(x,y) ((x)<<((y)<<1))
#define gbit(x,y) (((x)>>((y)<<1))&3)
#define cbit(x,y) ((x)&(~(3<<((y)<<1))))


int n, m, tots, slst[maxst];
bool mp[maxn][maxn];
dint f[2][maxst];


void dfsState(int l, int c, int z) {
if (l == m + 1) {
if (!c)
slst[tots ++] = z;
}
else {
dfsState(l + 1, c, z);
dfsState(l + 1, c + 1, z | mbit(1, l));
if (c)
dfsState(l + 1, c - 1, z | mbit(2, l));
}
}
void preState() {
tots = 0;
dfsState(0, 0, 0);
sort(slst, slst + tots);
}
inline int fState(int s) {
register int ret(lower_bound(slst, slst + tots, s) - slst);
if (slst[ret] != s)
puts(“naive”);
return ret;
}


#define inc(a,b) (a+=b)
inline int brv(int x) {
if (!x)
return 0;
else
return (x == 1) ? 1 : -1;
}


bool isEnd(int s, int y) {
for (int i = 0; i < y; ++ i)
if (gbit(s, i))
return 0;
for (int i = y + 2; i <= m; ++ i)
if (gbit(s, i))
return 0;
return 1;
}
inline int mergePlug(int s, int y) {
int p, c;
if (gbit(s, y) != gbit(s, y + 1)) {
s = cbit(s, y);
s = cbit(s, y + 1);
return fState(s);
}
else if (gbit(s, y) == 1) {
for (c = 1, p = y + 1; c; ++ p, c += brv(gbit(s, p)));
s = cbit(s, y);
s = cbit(s, y + 1);
s = cbit(s, p);
return fState(s | mbit(1, p));
}
else {
for (c = -1, p = y; c; – p, c += brv(gbit(s, p)));
s = cbit(s, y);
s = cbit(s, y + 1);
s = cbit(s, p);
return fState(s | mbit(2, p));
}
}
inline int extPlugRight(int s, int y) {
s |= mbit(gbit(s, y), y + 1);
s = cbit(s, y);
return fState(s);
}
inline int extPlugDown(int s, int y) {
s |= mbit(gbit(s, y + 1), y);
s = cbit(s, y + 1);
return fState(s);
}
inline int forkPlug(int s, int y) {
s |= mbit(1, y);
s |= mbit(2, y + 1);
return fState(s);
}
inline int nextRow(int s) {
int r(0);
for (int i = 0; i < m; ++ i)
r |= mbit(gbit(s, i), i + 1);
return fState(r);
}


dint dp() {
int cur(0), prv(1);
dint ans;
memset(f, 0, sizeof(f));
f[cur][0] = 1;
for (int x = 0; x < n; ++ x) {
for (int y = 0; y < m; ++ y) {
if (mp[x][y])
ans = 0;
swap(cur, prv);
memset(f[cur], 0, sizeof(f[cur]));
for (int i = 0; i < tots; ++ i)
if (f[prv][i]) {
int s(slst[i]);;
if (mp[x][y]) {
if (gbit(s, y) && gbit(s, y + 1)) {
if (gbit(s, y) == 1 && gbit(s, y + 1) == 2) {
if (isEnd(s, y))
inc(ans, f[prv][i]);
}
else
inc(f[cur][mergePlug(s, y)], f[prv][i]);
}
else if (gbit(s, y)) {
inc(f[cur][i], f[prv][i]);
inc(f[cur][extPlugRight(s, y)], f[prv][i]);
}
else if (gbit(s, y + 1)) {
inc(f[cur][i], f[prv][i]);
inc(f[cur][extPlugDown(s, y)], f[prv][i]);
}
else
inc(f[cur][forkPlug(s, y)], f[prv][i]);
}
else {
if (!gbit(s, y) && !gbit(s, y + 1))
inc(f[cur][i], f[prv][i]);
}
}
}
swap(cur, prv);
memset(f[cur], 0, sizeof(f[cur]));
for (int i = 0; i < tots; ++ i)
if (f[prv][i] && !gbit(slst[i], m))
inc(f[cur][nextRow(slst[i])], f[prv][i]);
}
return ans;
}


int main() {
#ifndef ONLINE_JUDGE
freopen(“in.txt”, “r”, stdin);
#endif


scanf("%d%d", &amp;n, &amp;m);
for (int i = 0; i &lt; n; ++ i) {
	char g[maxn];
	scanf("%s", g);
	for (int j = 0; j &lt; m; ++ j)
		mp[i][j] = (g[j] == '.');
}
preState();
printf(lld "\n", dp());



}