POJ 1739：Tony's Tour

#include<queue>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int mn=177147;
int i;
struct na{
    int x,z;
    na(int xx,int zz):x(xx),z(zz){}
};
int n,m,x,y,z,a[21],k,en,p1,p2;
char u[100];
bool map[21][21];
long long f[2][mn+1],ans;
int v[2][mn+1];
int re[21][21];
queue <na> q;
inline int gx(int x,int q1,int q2){k=0;for (register int i=m+1;i;i--) k=k*3+(i==x?q1:(i==x+1?q2:a[i]));return k;}
inline void up(int x,int z,long long lj){
    x++;
    k=x%2;
    if (v[k][z]!=x) v[k][z]=x,f[k][z]=0,q.push(na(x,z));
    f[k][z]+=lj;
}
int main(){
    register int i,j;
    while(scanf("%d%d",&n,&m)!=EOF){
        if (n==0&&m==0) break;
        ans=0;
        memset(map,0,sizeof(map));memset(v,0,sizeof(v));memset(re,0,sizeof(re));memset(f,0,sizeof(f));
        for (i=1;i<=n;i++){
            scanf("%s",&u);
            for (j=1;j<=m;j++)
            map[j][n-i+3]=u[j-1]==‘.‘;
        }
        n+=2;
        en=n*m-1;
        map[1][2]=1;map[m][2]=1;
        for (i=1;i<=m;i++) map[i][1]=1;
        while(!map[en%m+1][en/m+1]) en--;
        f[0][0]=v[0][0]=1;
        q.push(na(0,0));
        while(!q.empty()){
            na no=q.front();q.pop();
            long long an=f[no.x%2][no.z];
            if(no.x%m==0) no.z*=3;
            x=no.x%m+1;y=no.x/m+1;
            for (i=1;i<=m+1;i++) a[i]=0;
            for (i=1,j=no.z;j;i++,j/=3) a[i]=j%3;
            if (!map[x][y])up(no.x,gx(x,0,0),an);else
            if (a[x]==1&&a[x+1]==2){
                if (no.x==en) ans+=an;
            }else if (a[x]==2&&a[x+1]==1) up(no.x,gx(x,0,0),an);else
                if (a[x]==0&&a[x+1]==0){
                if (map[x][y+1]&&map[x+1][y]) up(no.x,gx(x,1,2),an);
            }else if (a[x]==0){
                if (map[x+1][y]) up(no.x,gx(x,0,a[x+1]),an);
                if (map[x][y+1]) up(no.x,gx(x,a[x+1],0),an);
            }else if (a[x+1]==0){
                if (map[x+1][y]) up(no.x,gx(x,0,a[x]),an);
                if (map[x][y+1]) up(no.x,gx(x,a[x],0),an);
            }else if (a[x]==a[x+1]){
                p1=p2=0;
                if (a[x]==1)
                for (j=0,i=x+2;i<=m;i++){
                    if (a[i]==1) j--;
                    if (a[i]==2) j++;
                    if (j>0&&!p1) p1=i,j--;
                    if (j>0&&p1){p2=i;break;}
                }else
                for (j=0,i=x-1;i;i--){
                    if (a[i]==1) j++;
                    if (a[i]==2) j--;
                    if (j>0&&!p2) p2=i,j--;
                    if (j>0&&p2){p1=i;break;}
                }
                a[p1]=1;a[p2]=2;up(no.x,gx(x,0,0),an);
            }
        }
        printf("%I64d\n",ans);
    }
}