洛谷 2147 SDOI2008 Cave 洞穴勘测

【题解】

　　动态树模板题，只要求维护森林的连通性，直接上板子即可。

 #include<cstdio>
 #include<algorithm>
 #define N 500010
 #define ls (c[u][0])
 #define rs (c[u][1])
 using namespace std;
 int n,m;
 inline int read(){
     int k=,f=; char c=getchar();
     while(c<''||c>'')c=='-'&&(f=-),c=getchar();
     while(''<=c&&c<='')k=k*+c-'',c=getchar();
     return k*f;
 }
 struct Link_Cut_Tree{
     int top,c[N][],fa[N],rev[N],q[N];
     inline void pushdown(int u){if(rev[u]) rev[ls]^=,rev[rs]^=,rev[u]^=,swap(ls,rs);}
     inline bool isroot(int u){return c[fa[u]][]!=u&&c[fa[u]][]!=u;}
     inline bool which(int u){return c[fa[u]][]==u;}
     void rotate(int u){
         int f=fa[u],gf=fa[f],wh=which(u);
         if(!isroot(f)){c[gf][which(f)]=u;}
         fa[u]=gf; fa[f]=u; fa[c[u][wh^]]=f;
         c[f][wh]=c[u][wh^]; c[u][wh^]=f;
     }
     void splay(int u){
         top=; q[top]=u;
         for(int i=u;!isroot(i);i=fa[i]) q[++top]=fa[i];
         for(int i=top;i;i--) pushdown(q[i]);
         while(!isroot(u)){
             if(!isroot(fa[u])) rotate(which(u)==which(fa[u])?fa[u]:u);
             rotate(u);
         }
     }
     void access(int u){for(int son=;u;son=u,u=fa[u]) splay(u),c[u][]=son;}
     void makeroot(int u){
         access(u); splay(u); rev[u]^=;
     }
     int find(int u){
         access(u); splay(u);
         while(ls) u=ls; return u;
     }
     void split(int x,int y){
         makeroot(x); access(y); splay(y);
     }
     void cut(int x,int y){
         split(x,y);
         if(c[y][]==x) c[y][]=,fa[x]=;
     }
     void link(int x,int y){
         makeroot(x); fa[x]=y;
     }
 }t;
 int main(){
     n=read(); m=read();
     while(m--){
         char c=getchar();
         while(c!='C'&&c!='D'&&c!='Q') c=getchar();
         char c2=getchar();
         while(c2!=' ') c2=getchar();
         int x=read(),y=read(),xrt=t.find(x),yrt=t.find(y);
         if(c=='C') if(xrt!=yrt) t.link(x,y);
         if(c=='D') if(xrt==yrt) t.cut(x,y);
         if(c=='Q') puts(xrt==yrt?"Yes":"No");
     }
     return ;
 }