bzoj 1210 [HNOI2004] 邮递员 插头dp

插头dp板子题？？

搞了我一晚上，还tm全是抄的标程。。

还有高精，哈希混入，还是我比较弱，orz各种dalao

有不明白的可以去看原论文。。

#include<cstdio>#include<cstring>#include<iostream>#include<algorithm>#include<cmath>#define base (int)1e9#define maxh 2650using namespace std;int n,m;int get(int s,int x){return (s>>((x-1)<<1))&3;}//查询对于状态s,第x位的状态. 三进制,所以左移一位.&3,得0,1,2 void change(int &s,int x,int y){int w=(x-1)<<1;s&=~(3<<w);s|=y<<w;}//将s状态的第x位改为y int find(int s,int x){for(int i=x,d=0,pos=get(s,x)==1?1:-1;;i+=pos){int nn=get(s,i);if(nn==1) d++; if(nn==2) d--;if(!d) return i;}}//找与该位匹配的括号 struct bignum{//高精没啥好说的... int a[5];void clear(){memset(a,0,sizeof a);}bignum(){clear();}void set(int x){clear();while(x){a[++a[0]]=x%base;x/=base;}}void print(){printf("%d",a[a[0]]);for(int i=a[0]-1;i>0;i--)printf("%09d",a[i]);}bignum operator + (bignum b){static bignum c;c.clear();c.a[0]=max(a[0],b.a[0])+1;for(int i=1;i<=c.a[0];i++){c.a[i]+=a[i]+b.a[i];c.a[i+1]+=c.a[i]/base;c.a[i]%=base;}while(!c.a[c.a[0]])c.a[0]--;return c;}void operator += (bignum b){*this=*this+b;}void operator = (int x){set(x);}}ans;struct hashtable{//骚骚的哈希 int key[maxh];int cnt,hash[maxh];bignum val[maxh];void clear(){memset(key,-1,sizeof key);memset(hash,0,sizeof hash);memset(val,0,sizeof val);cnt=0;}void newnode(int i,int x){hash[i]=++cnt;key[cnt]=x;}bignum & operator[](const int hh){int k;for(int i=hh%maxh;;i++){if(i==maxh)i=0;if(!hash[i]) newnode(i,hh);if(key[hash[i]]==hh){k=hash[i]; break;}}return val[k];}}f[2];int now,last;void dp(int i,int j){//插头dp now^=1;last^=1;int tot=f[last].cnt;f[now].clear();for(int k=1,x,y;k<=tot;k++){int s=f[last].key[k];bignum vv=f[last].val[k];x=get(s,j); y=get(s,j+1);if(!x&&!y){if(i!=n&&j!=m){change(s,j,1);change(s,j+1,2);f[now][s]+=vv;}}else if(x==1&&y==1){change(s,find(s,j+1),1);change(s,j,0); change(s,j+1,0);f[now][s]+=vv;} else if(x==2&&y==2){change(s,find(s,j),2);change(s,j,0); change(s,j+1,0);f[now][s]+=vv;}else if(x==1&&y==2){if(i==n&&j==m) ans+=vv;}else if(x==2&&y==1){change(s,j,0); change(s,j+1,0);f[now][s]+=vv;}else if(x){if(i!=n) f[now][s]+=vv;if(j!=m){change(s,j,0);change(s,j+1,x);f[now][s]+=vv;}}else if(y){if(j!=m) f[now][s]+=vv;if(i!=n){change(s,j+1,0);change(s,j,y);f[now][s]+=vv;}}}}int main(){    freopen("postman.in","r",stdin);    freopen("postman.out","w",stdout);scanf("%d%d",&n,&m);if(n==1||m==1){printf("1\n");return 0;}if(n<m)swap(n,m);f[0][0]=1;now=0;last=1;for(int i=1;i<=n;i++){for(int j=1;j<=m;j++)dp(i,j);if(i!=n)for(int j=1,k=f[now].cnt;j<=k;j++)f[now].key[j]<<=2;}ans+=ans;ans.print();return 0;}