URAL 1519 Formula 1

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
const int maxn = 15;
const int HASH = 30007;
const int SIZE = 1000010;
typedef long long LL;
int N,M,maze[maxn][maxn],code[maxn],ch[maxn],ex,ey;
char b[maxn];

struct Hashmap{
int e,first[HASH],next[SIZE];
LL state[SIZE],f[SIZE];

void init(){
e = 0;
memset(first,-1,sizeof(first));
}

void push(LL st,LL ans){
int h = st%HASH;
for(int i = first[h];i != -1;i = next[i])
if(state[i] == st){
f[i] += ans;
return;
}
state[e] = st;
f[e] = ans;
next[e] = first[h];
first[h] = e++;
}
}dp[2];

void update(int *code,int len){
for(int i = len;i >= 1;i--)
code[i] = code[i-1];
code[0] = 0;
}

void decode(int *code,int len,LL st){
for(int i = len;i >= 0;i--){
code[i] = st&7;
st >>= 3;
}
}

LL encode(int *code,int len){
int cnt = 1;
memset(ch,-1,sizeof(ch));
ch[0] = 0;
LL st = 0;
for(int i = 0;i <= len;i++){
if(ch[code[i]] == -1){
ch[code[i]] = cnt++;
}
code[i] = ch[code[i]];
st <<= 3;
st |= code[i];
}
return st;
}

void dpblank(int i,int j,int now,int pre){
int left,up,t;
for(int k = 0;k < dp[pre].e;k++){
decode(code,M,dp[pre].state[k]);
left = code[j-1],up = code[j];

if(left && up){
if(left == up){
if(i == ex && j == ey){
code[j-1] = code[j] = 0;
if(j == M)  update(code,M);
dp[now].push(encode(code,M),dp[pre].f[k]);
}
}
else{
code[j-1] = code[j] = 0;
for(t = 0;t <= M;t++){
if(code[t] == up)   code[t] = left;
}
if(j == M)  update(code,M);
dp[now].push(encode(code,M),dp[pre].f[k]);
}
}else if((!left && up) ||(left && !up)){
if(left) t = left;
else    t = up;
if(maze[i][j+1]){
code[j-1] = 0,code[j] = t;
dp[now].push(encode(code,M),dp[pre].f[k]);
}
if(maze[i+1][j]){
code[j-1] = t,code[j] = 0;
if(j == M)  update(code,M);
dp[now].push(encode(code,M),dp[pre].f[k]);
}
}else{
if(maze[i+1][j] && maze[i][j+1]){
code[j-1] = code[j] = 13;
dp[now].push(encode(code,M),dp[pre].f[k]);
}
}
}
}

void dpblock(int i,int j,int now,int pre){
for(int k = 0;k < dp[pre].e;k++){
decode(code,M,dp[pre].state[k]);
code[j-1] = code[j] = 0;
if(j == M)  update(code,M);
dp[now].push(encode(code,M),dp[pre].f[k]);
}
}

int main()
{
while(scanf("%d%d",&N,&M) != EOF){
memset(maze,0,sizeof(maze));
ex = 0;
for(int i = 1;i <= N;i++){
scanf("%s",b+1);
for(int j = 1;j <= M;j++)
if(b[j] == '.') maze[ex=i][ey=j] = 1;
}
if(ex == 0){
printf("0\n");
continue;
}
int now = 0,pre = 1;
dp[now].init();
dp[now].push(0,1);
for(int i = 1;i <= N;i++){
for(int j = 1;j <= M;j++){
swap(now,pre);
dp[now].init();
if(maze[i][j])  dpblank(i,j,now,pre);
else            dpblock(i,j,now,pre);
}
}
LL ans = 0;
for(int i = 0;i < dp[now].e;i++)
ans += dp[now].f[i];
printf("%I64d\n",ans);
}
return 0;
}