bzoj2049: [Sdoi2008]Cave 洞穴勘测

这道题是裸的lct(link-cut-tree) 觉得自己讲的不是很好 推荐个博客吧

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int M=10007;
int read(){
int ans=0,f=1,c=getchar();
while(c<'0'||c>'9'){if(c=='-') f=-1; c=getchar();}
while(c>='0'&&c<='9'){ans=ans*10+(c-'0'); c=getchar();}
return ans*f;
}
int n,m;
int c[M][2],fa[M],rev[M];
bool isrt(int x){return c[fa[x]][0]!=x&&c[fa[x]][1]!=x;}
void revs(int x){
if(!x) return ;
rev[x]^=1; swap(c[x][0],c[x][1]);
}
void down(int x){
if(!rev[x]) return ; rev[x]=0;
revs(c[x][0]); revs(c[x][1]);
}
void rotate(int x){
int y=fa[x],z=fa[y],l=0,r=1;
if(c[y][1]==x) l=1,r=0;
if(!isrt(y)){
if(c[z][0]==y) c[z][0]=x;
else c[z][1]=x;
}
fa[x]=z; fa[y]=x; fa[c[x][r]]=y;
c[y][l]=c[x][r]; c[x][r]=y;
}
int st[M],top;
void splay(int x){
if(!x) return ;
st[++top]=x;for(int i=x;!isrt(i);i=fa[i]) st[++top]=fa[i];
while(top) down(st[top--]);
while(!isrt(x)){
int y=fa[x],z=fa[y];
if(!isrt(y)){
if(c[z][0]==y^c[y][0]==x) rotate(x);
else rotate(y);
}
rotate(x);
}
}
void acs(int x){
int y=x,t=0;
while(x){
splay(x);
c[x][1]=t;
t=x; x=fa[x];
}
splay(y);
}
void mrt(int x){acs(x);  revs(x);}
void link(int x,int y){mrt(x); fa[x]=y;}
void cut(int x,int y){mrt(x); acs(y); c[y][0]=fa[x]=0;}
int find(int x){
while(c[x][0]) down(x),x=c[x][0];
splay(x);
return x;
}
void push_ans(int x,int y){
mrt(x); acs(y);
if(find(y)==x) printf("Yes\n");
else printf("No\n");
}
int main()
{
char ch[15];
int x,y;
n=read(); m=read();
for(int i=1;i<=m;i++){
scanf("%s",ch); x=read(); y=read();
if(ch[0]=='C') link(x,y);
else if(ch[0]=='D') cut(x,y);
else push_ans(x,y);
//      for(int i=1;i<=n;++i)printf("%d %d(%d,%d) %d\n",i,fa[i],c[i][0],c[i][1],rev[i]);
}
return 0;
}