奇怪的树剖+zkw线段树
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
#define maxn 10000
#define max(x,y) x>=y?x:y
int n,M,fa[maxn],top[maxn],siz[maxn],hchild[maxn],deep[maxn],id[maxn],iid[maxn],tree[maxn<<2];
int pre[maxn],to[maxn],next[maxn],weight[maxn],wei[maxn],num=0,tip=0;
void clear()
{
memset(fa,0,sizeof(int));memset(top,0,sizeof(int));memset(siz,0,sizeof(int));
memset(deep,0,sizeof(int));memset(hchild,0,sizeof(int));memset(id,0,sizeof(int));
memset(iid,0,sizeof(int));memset(weight,0,sizeof(int));memset(wei,0,sizeof(int));
memset(tree,0,sizeof(int));memset(pre,0,sizeof(int));memset(to,0,sizeof(int));
memset(next,0,sizeof(int));
}
void addedge(int x,int y,int z)
{num++; next[num]=pre[x],pre[x]=num,to[num]=y,weight[num]=z;}
void swap(int &x,int &y){int c=x;x=y,y=c;}
void updata()
{
for(int i=M-1;i>=1;i--) tree[i]=max(tree[i<<1],tree[i<<1|1]);
}
int query(int x,int y)
{
int ans=0;
x+=M,y+=M;
x--,y++;
while(1)
{
if(x%2==0)ans=max(ans,tree[x+1]);
if(y%2==1)ans=max(ans,tree[y-1]);
x>>=1,y>>=1;
if(x+1==y) break;
}
return ans;
}
void dfs1(int father,int now,int depth)
{
int p=pre[now];
deep[now]=depth;
fa[now]=father;
//if(!p){siz[now]=1;return;}
while(p)
{
if(to[p]==father) {p=next[p];continue;}
dfs1(now,to[p],depth+1);
siz[now]+=siz[to[p]];
if(siz[to[p]]>siz[hchild[now]]) hchild[now]=to[p],wei[now]=weight[p];
p=next[p];
}
if(!siz[now]) siz[now]=1;
}
void dfs2(int father,int now,int tp,int weig)
{
int p=pre[now];
top[now]=tp;
id[now]=tip;
tree[tip+M]=weig,tip++;
if(!p) return;
if(hchild[now]) dfs2(now,hchild[now],tp,wei[now]);
while(p)
{
if(to[p]==father||to[p]==hchild[now]) {p=next[p];continue;}
dfs2(now,to[p],to[p],weight[p]);
p=next[p];
}
}
int ask_max(int u,int v)
{
int t1=top[u],t2=top[v],ans=0;
while(t1!=t2)
{
if(deep[u]<deep[v]){swap(u,v),swap(t1,t2);}
ans=max(ans,query(id[t1],id[u]));
u=fa[top[u]],t1=top[u];
}
if(u==v) return ans;
if(deep[u]<deep[v]){swap(u,v),swap(t1,t2);}
ans=max(ans,query(id[hchild[v]],id[u]));
return ans;
}
int main()
{
int m,temp1,temp2,temp3;
clear();
scanf("%d%d",&n,&m);
for(M=1;M<n;M<<=1);
for(int i=1;i<=n-1;i++)
{
scanf("%d%d%d",&temp1,&temp2,&temp3);
addedge(temp1,temp2,temp3);
addedge(temp2,temp1,temp3);
}
dfs1(1,1,1);
dfs2(1,1,1,0);
updata();
for(int i=1;i<=m;i++)
{
scanf("%d%d",&temp1,&temp2);
printf("%d\n",ask_max(temp1,temp2));
}
}
//零零散散的从今天中午一直调到下午六点，我从来没有试过把线段树和树剖和在一起写
//1.总是自己乱脑补一些奇怪的位运算，然而是不对的
//2.现在左移和右移打错导致调试了很久OTL
//3.那个邻接表啊蠢货，你一条边是双向标记的，叶节点pre自然不为零
//4.自己进行了小小的优化噢
