SPOJ QTREE Query on a tree(树链剖分-点更新-区间最值查询-入边)

题意：

操作1.更改第i条边权值

操作2.查询i->j的路径最大值

操作3 跳出

#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>
using namespace std;
const int maxn = 100005;

int dep[maxn],siz[maxn],fa[maxn],id[maxn],son[maxn],val[maxn],top[maxn];
int topw,head[maxn],cnt;
///dep 深度 siz个数 fa父 top祖 son重儿子 val值
/// e数组 初始入边 edge数组存边
struct Edge
{
int to,next;
} edge[maxn*2];
struct treex
{
int x,y,val;

} e[maxn];
void add(int u,int v )
{
edge[cnt].to=v;
edge[cnt].next=head[u];
head[u]=cnt++;
}
void dfs1(int u,int f,int d)
{
dep[u]=d;
siz[u]=1;
son[u]=0;
fa[u]=f;
for(int i =head[u];i!=-1;i=edge[i].next)
{
int v=edge[i].to;
if(v==fa[u])
continue;
dfs1(v,u,d+1);
siz[u]+=siz[v];
if(siz[son[u]]<siz[v])
son[u]=v;
}
}
void dfs2(int u,int tp)
{
top[u]=tp;
id[u]=++topw;
if(son[u])
dfs2(son[u],tp);
for(int i=head[u];i!=-1;i=edge[i].next)
{
int v=edge[i].to;
if(v==fa[u]||v==son[u])
continue;
dfs2(v,v);
}
}
struct node
{
int left,right,maxx;
}tree[maxn*4];
void push_up(int i)
{
tree[i].maxx=max(tree[i<<1].maxx,tree[i<<1|1].maxx);
}
void build(int i,int left,int right)
{
tree[i].left=left;
tree[i].right=right;
if(left==right)
{
tree[i].maxx=val[left];
return ;
}
int mid=(tree[i].left+tree[i].right)>>1;
build(i<<1,left,mid);
build(i<<1|1,mid+1,right);
push_up(i);
}
void update(int i,int aim,int w)
{
if(tree[i].left==tree[i].right&&tree[i].left==aim)
{
tree[i].maxx=w;
return ;
}

int mid=(tree[i].left+tree[i].right)>>1;
if(aim<=mid)
update(i<<1,aim,w);
else
update(i<<1|1,aim,w);
push_up(i);
}
int query(int i,int left,int right)
{
if(tree[i].left>=left&&tree[i].right<=right)
return tree[i].maxx;

int mid=(tree[i].left+tree[i].right)>>1;
if(right<=mid)
return query(i<<1,left,right);
else if(left>mid)
return query(i<<1|1,left,right);
else
return max(query(i<<1,left,mid),query(i<<1|1,mid+1,right));
}

int change(int u,int v)
{
int tpu=top[u],tpv=top[v];
int ans=0;
while(tpu!=tpv)
{
if(dep[tpu]<dep[tpv])
swap(u,v),swap(tpu,tpv);
ans=max(ans,query(1,id[tpu],id[u]));
u=fa[tpu];
tpu=top[u];
}
if(u!=v)
{
if(dep[u]>dep[v])
swap(u,v);
ans=max(ans,query(1,id[son[u]],id[v]));
}
return ans;
}
int main()
{
int n,m,s;
int t;
scanf("%d",&t);
while(t--)
{
scanf("%d",&n);
memset(head,-1,sizeof(head));
for(int i=1;i<n;i++)
{
scanf("%d%d%d",&e[i].x,&e[i].y,&e[i].val);
add(e[i].x,e[i].y);
add(e[i].y,e[i].x);
}
topw=0;
dfs1(1,0,1);
dfs2(1,1);
//将之前给出的边的权值，赋给点。
for(int i=1;i<n;i++)
{
if(dep[e[i].x] < dep[e[i].y])
swap(e[i].x,e[i].y);
val[id[e[i].x]] = e[i].val;
}
char op[10];
build(1,1,topw);
while(1)
{
scanf("%s",op);
if(op[0]=='Q')
{
int l,r;

scanf("%d%d",&l,&r);
printf("%d\n",change(l,r));

}
else if(op[0]=='C')
{
int x,y;
scanf("%d%d",&x,&y);
update(1,id[e[x].x],y);
}
else
break;
}
}
return 0;
}