洛谷P3038 [USACO11DEC]牧草种植Grass Planting

链接

　　https://www.luogu.org/problem/show?pid=3038

题解

　　呃裸题....

　　边化点然后LCT做就好了....没啥好说的

　　当然正解肯定是树链剖分，可以用树状数组或者线段树维护。（以后有时间写一下树状数组的）

代码

//LCT
#include <cstdio>
#include <algorithm>
#define maxn 500000
using namespace std;
int N, M;
struct node
{
	int w, rev, add;
	node *f, *ch[2];
}nd[maxn], *s[maxn];
inline int getwh(node *x)
{if(!x->f)return -1;if(x->f->ch[0]==x)return 0;if(x->f->ch[1]==x)return 1;return -1;}
inline bool isroot(node *x){return getwh(x)==-1;}
inline void join(node *x, node *y, int wh){if(x)x->f=y;if(y)y->ch[wh]=x;}
inline void rev(node *x){if(x)x->rev^=1;}
inline void add(node *x, int v){if(x)x->add+=v;}
inline void pushdown(node *x)
{
	if(x->rev)
	{
		swap(x->ch[0],x->ch[1]);
		rev(x->ch[0]),rev(x->ch[1]);
		x->rev=0;
	}
	if(x->add)
	{
		x->w+=x->add;
		add(x->ch[0],x->add),add(x->ch[1],x->add);
		x->add=0;
	}
}
inline void rotate(node *x)
{
	node *y=x->f, *z=y->f; int c=getwh(x);
	if(isroot(y))x->f=y->f;else join(x,z,getwh(y));
	join(x->ch[!c],y,c);join(y,x,!c);
}
inline void splay(node *x)
{
	node *y; int top=0;
	for(y=x;!isroot(y);y=y->f)s[++top]=y;s[++top]=y;
	for(;top;top--)pushdown(s[top]);
	while(!isroot(x))
	{
		y=x->f;
		if(isroot(y)){rotate(x);return;}
		if(getwh(x)^getwh(y))rotate(x);else rotate(y);
		rotate(x);
	}
}
inline void access(node *x)
{
	node *t=0;
	while(x)
	{
		splay(x);
		x->ch[1]=t;
		t=x,x=x->f;
	}
}
inline void makeroot(node *x){access(x);splay(x);rev(x);}
inline void link(node *x, node *y){makeroot(x);x->f=y;}
int main()
{
	int x, y, i;
	char t[5];
	node *a, *b;
	scanf("%d%d",&N,&M);
	for(i=1;i<N;i++)
	{
		scanf("%d%d",&x,&y);
		if(x>y)swap(x,y);
		link(nd+N+i,nd+x),link(nd+N+i,nd+y);
	}
	for(i=1;i<=M;i++)
	{
		scanf("%s%d%d",t,&x,&y);
		if(*t=='P')makeroot(nd+x),access(nd+y),splay(nd+y),add(nd+y,1);
		else
		{
			a=nd+x, b=nd+y;
			makeroot(a);access(b);splay(b);
			pushdown(a->ch[1]);
			printf("%d\n",a->ch[1]->w);
		}
	}
	return 0;
}