【BZOJ1036】【ZJOI2008】树的统计Count 树链剖分裸题

来源：互联网发布：淘宝禁止发布编辑：程序博客网时间：2024/04/27 07:26

题解：裸的，没什么好说的。

树链剖分不会的先理解一下重链轻链，然后直接扒我代码理解就行了。

贴代码：

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>#define N 30100#define inf 0x3f3f3f3fusing namespace std;struct KSD{int u,v,next;}e[N<<1];int head[N],cnt;void add(int u,int v){++cnt;e[cnt].u=u;e[cnt].v=v;e[cnt].next=head[u];head[u]=cnt;}int n,m;int w[N],tw[N];struct Segment_Tree{int l,r,x[2];}s[N<<2];int deep[N],pos[N],fa[N],son[N],top[N];int dfs1(int x,int p){int i,v,sum=1,ax=-inf;deep[x]=deep[p]+1;fa[x]=p;for(i=head[x];i;i=e[i].next){v=e[i].v;if(v==p)continue;int temp=dfs1(v,x);sum+=temp;if(ax<temp)ax=temp,son[x]=v;}return sum;}void dfs2(int x,int p,int r){int i,v;pos[x]=++cnt;top[x]=r;if(son[x])dfs2(son[x],x,r);for(i=head[x];i;i=e[i].next){v=e[i].v;if(v!=son[x]&&v!=p)dfs2(v,x,v);}}void pushup(int x){s[x].x[0]=s[x<<1].x[0]+s[x<<1|1].x[0];s[x].x[1]=max(s[x<<1].x[1],s[x<<1|1].x[1]);}void build(int note,int l,int r){s[note].l=l,s[note].r=r;if(l==r){s[note].x[0]=s[note].x[1]=w[l];return ;}int mid=l+r>>1;build(note<<1,l,mid);build(note<<1|1,mid+1,r);pushup(note);}void change(int note,int x,int y){if(s[note].l==s[note].r){s[note].x[0]=s[note].x[1]=y;return ;}int mid=s[note].l+s[note].r>>1;if(x<=mid)change(note<<1,x,y);else change(note<<1|1,x,y);pushup(note);}int QUERY(int note,int l,int r,int c){if(s[note].l==l&&r==s[note].r)return s[note].x[c];int mid=s[note].l+s[note].r>>1;if(r<=mid)return QUERY(note<<1,l,r,c);else if(l>mid)return QUERY(note<<1|1,l,r,c);else {if(c==0)return QUERY(note<<1,l,mid,0)+QUERY(note<<1|1,mid+1,r,0);else return max(QUERY(note<<1,l,mid,1),QUERY(note<<1|1,mid+1,r,1));}}int query(int a,int b,int c){int A,B,ans[2];ans[0]=0,ans[1]=-inf;for(A=top[a],B=top[b];A!=B;a=fa[A],A=top[a]){if(deep[A]<deep[B])swap(A,B),swap(a,b);if(c==0)ans[0]+=QUERY(1,pos[A],pos[a],0);else ans[1]=max(ans[1],QUERY(1,pos[A],pos[a],1));}if(deep[a]<deep[b])swap(a,b);if(c==0)return ans[0]+QUERY(1,pos[b],pos[a],0);else return max(ans[1],QUERY(1,pos[b],pos[a],1));}char opt[10];int main(){//freopen("test.in","r",stdin);//freopen("my.out","w",stdout);int i,a,b;scanf("%d",&n);for(i=1;i<n;i++){scanf("%d%d",&a,&b);add(a,b);add(b,a);}cnt=0;dfs1(1,0);dfs2(1,0,1);for(i=1;i<=n;i++)scanf("%d",&tw[i]),w[pos[i]]=tw[i];build(1,1,n);scanf("%d",&m);for(i=1;i<=m;i++){scanf("%s",opt);scanf("%d%d",&a,&b);if(opt[0]=='Q'){if(opt[1]=='S')printf("%d\n",query(a,b,0));else printf("%d\n",query(a,b,1));}else change(1,pos[a],b);}//fclose(stdin);//fclose(stdout);return 0;}

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