BZOJ 1018 线段树维护图连通性

用8个bool维护即可分别为LURU,LURD,LDRU,LDRD,LULD,RURD,Side[1],Side[2]即可。

Side表示这一块有没有接到右边。Merge一下就可以了。码农题，WA了一次，发现未初始化，就AC了。。

#include <cstdio>
inline int Min(int x,int y) {return x>y?y:x;}
inline void Swap(int &x,int &y) {int t=x;x=y;y=t;}
inline void Get_Int(int &x) 
{
    char ch=getchar(); x=0;
    while (ch<'0' || ch>'9') ch=getchar();
    while (ch>='0' && ch<='9') {x=x*10+ch-'0'; ch=getchar();}
}
//========================================
const int Maxn=100100;
struct Node 
{
    bool LURU,LURD,LDRU,LDRD,LULD,RURD,Side[3];
}Tree[Maxn<<2],Null;
int x1,y1,x2,y2,n;
char ch[20];
inline Node Merge(Node L,Node R)
{
    Node Ret; Ret=Null;
    Ret.Side[1]=R.Side[1],Ret.Side[2]=R.Side[2];
    if ((L.LURU&&R.LURU&&L.Side[1]) || (L.LURD&&R.LDRU&&L.Side[2])) Ret.LURU=true;
    if ((L.LDRD&&R.LDRD&&L.Side[2]) || (L.LDRU&&R.LURD&&L.Side[1])) Ret.LDRD=true;
    if ((L.LURU&&R.LURD&&L.Side[1]) || (L.LURD&&R.LDRD&&L.Side[2])) Ret.LURD=true;
    if ((L.LDRD&&R.LDRU&&L.Side[2]) || (L.LDRU&&R.LURU&&L.Side[1])) Ret.LDRU=true;
    if (L.LULD || (L.LURU&&L.LDRD&&R.LULD&&L.Side[1]&&L.Side[2])) Ret.LULD=true;
    if (R.RURD || (R.LURU&&R.LDRD&&L.RURD&&L.Side[1]&&L.Side[2])) Ret.RURD=true;
    return Ret;
}
void Build(int o,int l,int r)
{
     
    if (l==r)
    {
        Tree[o].LURU=Tree[o].LDRD=true;
        return;
    }
    int mid=(l+r)>>1;
    Build(o<<1,l,mid),Build(o<<1|1,mid+1,r);
    Tree[o]=Merge(Tree[o<<1],Tree[o<<1|1]);
}
void Modify_X(int o,int l,int r,int pos,bool kind)
{
    if (l==r)
    {
        Tree[o].LULD=Tree[o].RURD=Tree[o].LURD=Tree[o].LDRU=kind;
        return;
    }
    int mid=(l+r)>>1;
    if (pos<=mid) Modify_X(o<<1,l,mid,pos,kind); else Modify_X(o<<1|1,mid+1,r,pos,kind);
    Tree[o]=Merge(Tree[o<<1],Tree[o<<1|1]);
}
void Modify_Y(int o,int l,int r,int pos,int x,bool kind)
{
    if (l==r)
    {
        Tree[o].Side[x]=kind;
        return;
    }
    int mid=(l+r)>>1;
    if (pos<=mid) Modify_Y(o<<1,l,mid,pos,x,kind); else Modify_Y(o<<1|1,mid+1,r,pos,x,kind);
    Tree[o]=Merge(Tree[o<<1],Tree[o<<1|1]);
}
inline void Close()
{
    if (x1==x2) Modify_Y(1,1,n,Min(y1,y2),x1,false);
    if (y1==y2) Modify_X(1,1,n,y1,false);
}
inline void Open()
{
    if (x1==x2) Modify_Y(1,1,n,Min(y1,y2),x1,true);
    if (y1==y2) Modify_X(1,1,n,y1,true);
}
Node Query(int o,int l,int r,int p,int q)
{
    if (l==p && r==q)
    {
        Node Ret=Tree[o];
        return Ret;
    }
    int mid=(l+r)>>1;
    if (q<=mid) return Query(o<<1,l,mid,p,q);
    if (p>=mid+1) return Query(o<<1|1,mid+1,r,p,q);
    if (p<=mid && q>=mid+1)
        return Merge(Query(o<<1,l,mid,p,mid),Query(o<<1|1,mid+1,r,mid+1,q));
} 
inline bool Check()
{
    if (y1>y2) Swap(y1,y2),Swap(x1,x2);  
    Node Pre,Suf,Now;
    if (y1-1>=1) Pre=Query(1,1,n,1,y1-1); else Pre=Null;
    if (y2+1<=n) Suf=Query(1,1,n,y2+1,n); else Suf=Null;
    Now=Query(1,1,n,y1,y2);
    if (x1==x2) 
    {
        if ((x1==1) && ((Now.LURU) || (Pre.RURD&&Pre.Side[1]&&Pre.Side[2]&&Now.LDRU) || (Suf.LULD&&Now.Side[1]&&Now.Side[2]&&Now.LURD) || (Pre.RURD&&Suf.LULD&&Now.Side[1]&&Now.Side[2]&&Pre.Side[1]&&Pre.Side[2]&&Now.LDRD)))  return true;
        if ((x1==2) && ((Now.LDRD) || (Pre.RURD&&Pre.Side[1]&&Pre.Side[2]&&Now.LURD) || (Suf.LULD&&Now.Side[1]&&Now.Side[2]&&Now.LDRU) || (Pre.RURD&&Suf.LULD&&Now.Side[1]&&Now.Side[2]&&Pre.Side[1]&&Pre.Side[2]&&Now.LURU)))  return true;    
    } else
    {
        if ((x1==1 && x2==2) && ((Now.LURD) || (Pre.RURD&&Pre.Side[1]&&Pre.Side[2]&&Now.LDRD) || (Suf.LULD&&Now.Side[1]&&Now.Side[2]&&Now.LURU) || (Pre.RURD&&Suf.LULD&&Now.Side[1]&&Now.Side[2]&&Pre.Side[1]&&Pre.Side[2]&&Now.LDRU)))  return true;
        if ((x1==2 && x2==1) && ((Now.LDRU) || (Pre.RURD&&Pre.Side[1]&&Pre.Side[2]&&Now.LURU) || (Suf.LULD&&Now.Side[1]&&Now.Side[2]&&Now.LDRD) || (Pre.RURD&&Suf.LULD&&Now.Side[1]&&Now.Side[2]&&Pre.Side[1]&&Pre.Side[2]&&Now.LURD)))  return true;
    }
    return false;
}
inline void Ask() {if (Check()) puts("Y"); else puts("N");}
int main()
{
    // freopen("c.in","r",stdin);
    Get_Int(n); Build(1,1,n);
    Null.LURU=Null.LURD=Null.LDRU=Null.LDRD=Null.Side[1]=Null.Side[2]=Null.LULD=Null.RURD=false;
    while (scanf("%s",ch)!=EOF)
    {
        if (ch[0]=='E') break;
        Get_Int(x1),Get_Int(y1),Get_Int(x2),Get_Int(y2);
        if (ch[0]=='O') Open();
        if (ch[0]=='C') Close();
        if (ch[0]=='A') Ask();
    }
    return 0;
}