BZOJ 2243 树链剖分

学习了一下树链剖分。

相关文章：http://blog.sina.com.cn/s/blog_7a1746820100wp67.html

这题差不多算是模板题了吧。

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>using namespace std;#define maxn 100005struct SegTree{    int l,r;    int lc,rc;    int num;} tree[maxn<<2];int size[maxn],fa[maxn],dep[maxn],son[maxn];int top[maxn],tid[maxn],label;int head[maxn],to[maxn<<1],next[maxn<<1],edge,e[maxn][3];int root;int color[maxn],p[maxn];int LC,RC;void init(){    root=1;    memset(head,-1,sizeof(head));    fa[root]=dep[root]=label=edge=0;}inline void add(int u,int v){    to[edge]=v,next[edge]=head[u],head[u]=edge++;}inline void pushup(int rt){    int ls=rt<<1,rs=ls+1;    tree[rt].lc=tree[ls].lc;    tree[rt].rc=tree[rs].rc;    tree[rt].num=tree[ls].num+tree[rs].num;    if(tree[ls].rc==tree[rs].lc)        tree[rt].num--;}inline void pushdown(int rt){    if(tree[rt].num==1)    {        int ls=rt<<1,rs=ls+1;        tree[ls].num=tree[rs].num=1;        tree[ls].lc=tree[rs].lc=tree[ls].rc=tree[rs].rc=tree[rt].lc;    }}void build(int rt,int l,int r){    tree[rt].l=l,tree[rt].r=r;    if(l==r)    {        tree[rt].lc=tree[rt].rc=color[p[l]];        tree[rt].num=1;        return ;    }    int mid=(l+r)>>1;    build(rt<<1,l,mid);    build(rt<<1|1,mid+1,r);    pushup(rt);}void Find(int x){    size[x]=1,son[x]=0;    for(int i=head[x],v; ~i; i=next[i])    {        v=to[i];        if(v==fa[x]) continue;        fa[v]=x;        dep[v]=dep[x]+1;        Find(v);        size[x]+=size[v];        if(size[v]>size[son[x]])            son[x]=v;    }}void Connect(int x,int ancestor){    tid[x]=++label,top[x]=ancestor;    if(son[x]) Connect(son[x],ancestor);    for(int i=head[x],v; ~i; i=next[i])    {        v=to[i];        if(v==son[x]||v==fa[x]) continue;        Connect(v,v);    }}void update(int rt,int l,int r,int val){    if(tree[rt].l>=l&&tree[rt].r<=r)    {        tree[rt].num=1;        tree[rt].lc=tree[rt].rc=val;        return ;    }    int mid=(tree[rt].l+tree[rt].r)>>1;    pushdown(rt);    if(l<=mid) update(rt<<1,l,r,val);    if(r>mid) update(rt<<1|1,l,r,val);    pushup(rt);}int getsum(int rt,int l,int r){    if(l==tree[rt].l) LC=tree[rt].lc;    if(r==tree[rt].r) RC=tree[rt].rc;    if(tree[rt].l>=l&&tree[rt].r<=r)        return tree[rt].num;    int mid=(tree[rt].l+tree[rt].r)>>1;    pushdown(rt);    int ls=rt<<1,rs=ls+1;    int res=0,c1=-1,c2=-1;    if(l<=mid) res+=getsum(ls,l,r),c1=tree[ls].rc;    if(r>mid) res+=getsum(rs,l,r),c2=tree[rs].lc;    if(c1==c2&&c1!=-1) res--;    return res;}void change(int x,int y,int d){    int gx=top[x],gy=top[y];    while(gx!=gy)    {        if(dep[gx]<dep[gy])        {            swap(gx,gy);            swap(x,y);        }        update(1,tid[gx],tid[x],d);        x=fa[gx];        gx=top[x];    }    if(dep[x]>dep[y]) swap(x,y);    update(1,tid[x],tid[y],d);}int query(int x,int y){    int gx=top[x],gy=top[y];    int res=0;    int cx=-1,cy=-1;    while(gx!=gy)    {        if(dep[gx]<dep[gy])        {            swap(gx,gy);            swap(x,y);            swap(cx,cy);        }        res+=getsum(1,tid[gx],tid[x]);        if(cx==RC) res--;        cx=LC;        x=fa[gx];        gx=top[x];    }    if(dep[x]>dep[y]) swap(x,y),swap(cx,cy);    res+=getsum(1,tid[x],tid[y]);    if(cx==LC) res--;    if(cy==RC) res--;    return res;}int main(){    int n,m;    char op[5];    while(~scanf("%d%d",&n,&m))    {        init();        int a,b,c;        for(int i=1; i<=n; i++) scanf("%d",&color[i]);        for(int i=1; i<n; i++)        {            scanf("%d%d",&a,&b);            add(a,b);            add(b,a);        }        Find(root);        Connect(root,root);        for(int i=1; i<=n; i++) p[tid[i]]=i;        build(1,1,label);        while(m--)        {            scanf("%s",op);            if(op[0]=='Q')            {                scanf("%d%d",&a,&b);                printf("%d\n",query(a,b));            }            else            {                scanf("%d%d%d",&a,&b,&c);                change(a,b,c);            }        }    }    return 0;}