BZOJ 2588 Spoj 10628. Count on a tree

主席树+LCA

对于每个点，建一棵该点到根路径上的权值线段树，用主席树搞一搞，对于每个询问(a,b)，记c是他们的LCA，d是c父亲，用siz[a]+siz[b]-siz[c]-siz[d]查找即可- -

WA到吐血才发现自己lower_bound里面的cnt打成n了。。。QAQ

#include<cstdio>#include<cmath>#include<iostream>#include<algorithm>#define N 100005 using namespace std;int w[N], v[N], n, m, cnt, fa[N][20], dep[N], last[N]; struct edge{    int next,to;}e[N<<1];int e_cnt=0;void add(int a, int b){    e[++e_cnt]=(edge){last[a],b};    last[a]=e_cnt;}struct node{    node *ch[2];    int cnt, siz;    node()    {        ch[0]=ch[1]=NULL;        cnt=siz=0;    }    void update()    {        siz=cnt;        if(ch[0])siz+=ch[0]->siz;        if(ch[1])siz+=ch[1]->siz;    }}*root[N]={NULL}, *null=new node(), q[2000000];int q_cnt=0;void inser(node *&x, node *&y, int l, int r, int pos){    if(x==NULL)x=null;    y=&q[++q_cnt];    if(l==r)    {        *y=*x;        y->siz++;        y->cnt++;        return;    }    int mid=(l+r)>>1;    if(pos<=mid)    {        y->ch[1]=x->ch[1];        inser(x->ch[0],y->ch[0],l,mid,pos);        y->update();    }    else     {        y->ch[0]=x->ch[0];        inser(x->ch[1],y->ch[1],mid+1,r,pos);        y->update();    }}void dfs(int x){    inser(root[fa[x][0]],root[x],1,cnt,w[x]);    dep[x]=dep[fa[x][0]]+1;    for(int i = 1; (1<<i)<dep[x]; i++)        fa[x][i]=fa[fa[x][i-1]][i-1];    for(int i = last[x]; i; i=e[i].next)    {        if(e[i].to!=fa[x][0])        {            fa[e[i].to][0]=x;            dfs(e[i].to);        }    }}int LCA(int a, int b){    if(dep[a]<dep[b])swap(a,b);    for(int d=dep[a]-dep[b], i = 0; d; i++)        if(d&(1<<i))a=fa[a][i],d^=(1<<i);    for(int i = 19; i >= 0; i--)    {        if(fa[a][i]!=fa[b][i])            a=fa[a][i],b=fa[b][i];    }    if(a==b)return a;    else return fa[a][0];}int query(node *a, node *b, node *c, node *d, int l, int r, int k){    if(a==NULL)a=null;    if(b==NULL)b=null;    if(c==NULL)c=null;    if(d==NULL)d=null;    if(l==r)return v[l];    int size = 0;    if(a->ch[0])size+=a->ch[0]->siz;    if(b->ch[0])size+=b->ch[0]->siz;    if(c->ch[0])size-=c->ch[0]->siz;    if(d->ch[0])size-=d->ch[0]->siz;    int mid=(l+r)>>1;    if(k<=size)return query(a->ch[0],b->ch[0],c->ch[0],d->ch[0],l,mid,k);    else return query(a->ch[1],b->ch[1],c->ch[1],d->ch[1],mid+1,r,k-size);}int solve(int a, int b, int k){    int c=LCA(a,b), d=fa[c][0];    return query(root[a],root[b],root[c],root[d],1,cnt,k);}int main(){    scanf("%d%d",&n,&m);    for(int i = 1; i <= n; i++)    {        scanf("%d",&w[i]);        v[i]=w[i];    }    for(int i = 1; i < n; i++)    {        int a, b;        scanf("%d%d",&a,&b);        add(a,b);add(b,a);    }    sort(v+1,v+n+1);    cnt = unique(v+1,v+n+1)-v-1;    for(int i = 1; i <= n; i++)    {        w[i]=lower_bound(v+1,v+cnt+1,w[i])-v;    }    dfs(1);    for(int i = 1, ans = 0; i <= m; i++)    {        int a, b, c;        scanf("%d%d%d",&a,&b,&c);        a^=ans;        ans=solve(a,b,c);        printf("%d",ans);           if(i!=m)printf("\n");       }}