bzoj2243-染色(动态树lct)

解析：增加三个变量lc(最左边的颜色),rc(最右边的颜色),sum(连续相同颜色区间段数)。然后就是区间合并的搞法。我就不详细解释了，估计你已经想到

如何做了。

代码

#include<cstdio>
#include<cstring>
#include<string>
#include<vector>
#include<algorithm>
using namespace std;
const int maxn=;
int N,M,C[maxn];
struct lct
{
    lct *fa,*son[];
    int rev,c,setc,lc,rc,sum;
};
struct LCT
{
    lct data[maxn];
    lct *null;
    void init(int Size=maxn-) //初始化
    {
        null=data; //null指向首元素
        for(int i=;i<=Size;i++)
        {
            data[i].son[]=data[i].son[]=data[i].fa=null;
            data[i].rev=;
            data[i].c=data[i].lc=data[i].rc=C[i];
            data[i].setc=-;
            data[i].sum=;
        }
        null->c=null->lc=null->rc=-;
        null->sum=;
    }
    void push_rev(lct* x)
    {
        if(x==null) return;
        x->rev=!x->rev;
        swap(x->son[],x->son[]);
        swap(x->lc,x->rc);
    }
    void push_setc(lct* x,int setc)
    {
        if(x==null) return;
        x->c=setc;
        x->setc=setc;
        x->lc=setc;
        x->rc=setc;
        x->sum=;
    }
    void pushdown(lct* x)
    {
        if(x->setc!=-)
        {
            push_setc(x->son[],x->setc);
            push_setc(x->son[],x->setc);
            x->setc=-;
        }
        if(x->rev)
        {
            push_rev(x->son[]);
            push_rev(x->son[]);
            x->rev=;
        }
    }
    void pushup(lct* x)
    {
        if(x==null) return;
        x->sum=;
        if(x->son[]!=null)
        {
            x->sum+=x->son[]->sum;
            if(x->son[]->rc==x->c) x->sum--;
        }
        if(x->son[]!=null)
        {
            x->sum+=x->son[]->sum;
            if(x->son[]->lc==x->c) x->sum--;
        }
        x->lc=x->c;
        if(x->son[]!=null) x->lc=x->son[]->lc;
        x->rc=x->c;
        if(x->son[]!=null) x->rc=x->son[]->rc;
    }
    bool Same(lct* x,lct* &y) //判断x和x的父亲是否在同一树里
    {
        return (y=x->fa)!=null&&(y->son[]==x||y->son[]==x);
    }
    void Rotate(lct* x,int d) //翻转
    {
        lct* y=x->fa; //x的父亲
        y->son[d^]=x->son[d];
        if(x->son[d]!=null) x->son[d]->fa=y; //x的子节点的父亲指向y
        x->fa=y->fa;  //连接
        if(y->fa->son[]==y) x->fa->son[]=x;
        else if(y->fa->son[]==y) x->fa->son[]=x;
        x->son[d]=y;
        y->fa=x;
    }
    void Splay(lct* x)
    {
        pushdown(x); //清除标记
        lct* y;
        while(Same(x,y)) //没有到树的最顶点
        {
            pushdown(y);
            pushdown(x);
            Rotate(x,y->son[]==x); //翻转
            pushup(y);
            pushup(x);
        }
    }
    lct* Access(lct* u)  //打通路径,返回的是根
    {
        lct *v=null;
        for(;u!=null;u=u->fa)
        {
            Splay(u);
            u->son[]=v;
            pushup(v=u);
        }
        return v;
    }
    lct* GetRoot(lct* x) //得到根
    {
        for(x=Access(x);pushdown(x),x->son[]!=null;x=x->son[]) pushup(x);
        return x;
    }
    void MakeRoot(lct* x) //使x成为根
    {
        Access(x);
        Splay(x);
        push_rev(x);
    }
    void Link(lct* x,lct* y) //连接两个点
    {
        MakeRoot(x);
        x->fa=y;
        Access(x);
    }
    void Cut(lct* x,lct* y) //断开两个点
    {
        MakeRoot(x);
        Access(y);
        Splay(y);
        y->son[]->fa=null;
        y->son[]=null;
    }
    void SetC(lct* x,lct* y,int setc)
    {
        MakeRoot(x);
        push_setc(Access(y),setc);
    }
    int Query(lct* x,lct* y)
    {
        MakeRoot(x);
        Access(y);
        Splay(y);
        return y->sum;
    }
}A;
int main()
{
    scanf("%d%d",&N,&M);
    for(int i=;i<=N;i++) scanf("%d",&C[i]);
    A.init(N);
    int x,y;
    for(int i=;i<N;i++)
    {
        scanf("%d%d",&x,&y);
        A.Link(A.data+x,A.data+y);
    }
    char op[];
    int c;
    while(M--)
    {
        scanf("%s%d%d",op,&x,&y);
        if(op[]=='C') scanf("%d",&c);
        if(op[]=='C') A.SetC(A.data+x,A.data+y,c);
        else printf("%d\n",A.Query(A.data+x,A.data+y));
    }
    return ;
}