Ural 1519 Formula 1( 插头dp )

1519. Formula 1

Time limit: 1.0 second
Memory limit: 64 MB

Background

Regardless
of the fact, that Vologda could not get rights to hold the Winter
Olympic games of 20**, it is well-known, that the city will conduct one
of the Formula 1 events. Surely, for such an important thing a new race
circuit should be built as well as hotels, restaurants, international
airport - everything for Formula 1 fans, who will flood the city soon.
But when all the hotels and a half of the restaurants were built, it
appeared, that at the site for the future circuit a lot of gophers lived
in their holes. Since we like animals very much, ecologists will never
allow to build the race circuit over the holes. So now the mayor is
sitting sadly in his office and looking at the map of the circuit with
all the holes plotted on it.

Problem

Who
will be smart enough to draw a plan of the circuit and keep the city
from inevitable disgrace? Of course, only true professionals -
battle-hardened programmers from the first team of local technical
university!.. But our heroes were not looking for easy life and set much
more difficult problem: "Certainly, our mayor will be glad, if we find
how many ways of building the circuit are there!" - they said.

It should be said, that the circuit in Vologda is going to be rather simple. It will be a rectangle N*M
cells in size with a single circuit segment built through each cell.
Each segment should be parallel to one of rectangle's sides, so only
right-angled bends may be on the circuit. At the picture below two
samples are given for N = M = 4 (gray squares mean gopher
holes, and the bold black line means the race circuit). There are no
other ways to build the circuit here.

#include <bits/stdc++.h>
using namespace std ;
const int N = 15 ;
const int M = 30007 ;
const int MAXN = 1000010;
int n , m ;
int maze

;
int code
;
int ch
;
int ex , ey ;

struct HASHMAP {
int head[M] , next[MAXN] , tot  ;
long long st[MAXN] , f[MAXN] ;
void init() {
memset( head , -1 , sizeof head ) ;
tot = 0 ;
}
void push( long long state , long long ans ) {
int u = state % M ;
for( int i = head[u] ; ~i ; i = next[i] ) {
if( st[i] == state ) {
f[i] += ans ; return ;
}
}
st[tot] = state ;
f[tot] = ans ;
next[tot] = head[u] ;
head[u] = tot++ ;
}
} mp[2] ;

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

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

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

void dpblank( int i , int j , int cur ) {
int left , up ;
for( int k = 0 ; k < mp[cur].tot ; ++k ) {
decode( code , m , mp[cur].st[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 ) shift(code,m);
mp[cur^1].push( encode(code,m) , mp[cur].f[k] );
}
}else {
code[j-1] = code[j] = 0 ;
for( int t = 0 ; t <= m ; ++t ) {
if( code[t] == up )
code[t] = left ;
}
if( j == m ) shift( code,m );
mp[cur^1].push(encode(code,m),mp[cur].f[k]) ;
}
}
else if( ( left && ( !up ) ) || ( up && (!left ) ) ) {
int  t ;
if( left ) t = left ;
else t = up ;
if( maze[i][j+1] ) {
code[j-1] = 0 ;
code[j] = t ;
mp[cur^1].push( encode(code,m) , mp[cur].f[k] ) ;
}
if( maze[i+1][j] ) {
code[j-1] = t ;
code[j] = 0 ;
if( j == m ) shift( code , m );
mp[cur^1].push(encode(code,m),mp[cur].f[k]);

}
}
else {
if( maze[i][j+1] && maze[i+1][j] ) {
code[j-1] = code[j] = 13 ;
mp[cur^1].push( encode(code,m),mp[cur].f[k]);
}
}
}
}
void dpblock( int i , int j , int cur ) {
for( int k = 0 ; k < mp[cur].tot ; ++k ) {
decode( code , m , mp[cur].st[k] );
code[j-1] = code[j] = 0 ;
if( j == m ) shift( code , m );
mp[cur^1].push( encode(code,m) , mp[cur].f[k] );
}
}

void Solve() {
int v = 0 ;
mp[v].init();
mp[v].push(0,1);
for( int i = 1 ; i <= n ; ++i ) {
for( int j = 1 ; j <= m ; ++j ) {
mp[v^1].init() ;
if( maze[i][j] ) dpblank( i , j , v ) ;
else dpblock( i , j , v );
v ^= 1 ;
}
}
long long ans = 0 ;
for( int i = 0 ; i < mp[v].tot ; ++i )
ans += mp[v].f[i];
printf("%lld\n",ans);
}

char s[20];

int main () {
while( ~scanf("%d%d",&n,&m) ) {
ex = 0 ;
memset( maze , 0 , sizeof maze ) ;
for( int i = 1 ; i <= n ; ++i ) {
scanf("%s",s);
for( int j = 0 ; j < m ; ++j ) {
if( s[j] == '.' ) {
ex = i , ey = j + 1 ;
maze[i][j+1] = 1 ;
}
}
}
if( !ex ) { puts("0"); continue ; }
else Solve();
}
return 0 ;
}

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