SPOJ QTREE 树链剖分

#include<queue>
#include<stack>
#include<cmath>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#define INF 99999999
#define ll __int64
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
using namespace std;
const int MAXN = 10010;
struct node
{
int to;
int v;
int next;
}edge[MAXN*3];
int pre[MAXN],ind,top[MAXN],fa[MAXN],son[MAXN],w[MAXN],deq[MAXN],siz[MAXN],fn;
int tree[MAXN<<2],val[MAXN][3],n;
void add(int x,int y,int z)
{
edge[ind].to = y;
edge[ind].v = z;
edge[ind].next = pre[x];
pre[x] = ind++;
}

//第一次搜索找出siz[],son[],deq[],fa[]
void dfs1(int rt,int pa,int d)
{
deq[rt] = d;
son[rt] = 0;
fa[rt] = pa;
siz[rt] = 1;
int i;
for(i=pre[rt]; i!=-1; i=edge[i].next){
int t = edge[i].to;
if(t != fa[rt]){
dfs1(t,rt,d+1);
siz[rt] += siz[t];
if(siz[son[rt]] < siz[t]){//如果父节点的son[rt]的iz[]小于子节点的siz[]更新son[]
son[rt] = t;
}
}
}
}

//第二次搜索找到w[],top[]
void dfs2(int rt,int tp)
{
top[rt] = tp;
w[rt] = ++fn;

if(son[rt] != 0)
dfs2(son[rt],tp);//如果当前父节点纯在son 那么为了让链在线段树中连续 先对son[]进行搜索，并且重边顶端的点相同。

for(int i=pre[rt]; i!=-1; i=edge[i].next){
int t = edge[i].to;
if(t != fa[rt] && son[rt] != t){
dfs2(t,t);
}
}
}
void updata(int p,int v,int l,int r,int rt)
{
if(l == r){
tree[rt] = v;
return ;
}
int m = (l+r)/2;
if(m >= p){
updata(p,v,lson);
}
else {
updata(p,v,rson);
}
tree[rt] = max(tree[rt<<1],tree[rt<<1|1]);
}
int query(int L,int R,int l,int r,int rt)
{
if(L<=l && r<=R){
return tree[rt];
}
int m = (l+r)/2;
int ans = 0;
if(m >= L){
ans = max(ans,query(L,R,lson));
}
if(m < R){
ans = max(ans,query(L,R,rson));
}
return ans;
}
int lca(int x,int y)
{
int f1,f2;
int ans = 0;
while(top[x] != top[y])
{
if(deq[top[x]] < deq[top[y]]){
swap(x,y);
}
ans = max(ans,query(w[top[x]],w[x],1,fn,1));

x = fa[top[x]];
}

if(x == y)
return ans;

if(deq[x] < deq[y]){
swap(x,y);
}
return max(ans,query(w[son[y]],w[x],1,fn,1))    ;
}
int main()
{
int i,j,t;
scanf("%d",&t);
while(t--)
{
scanf("%d",&n);
ind = 1;
memset(pre,-1,sizeof(pre));
for(i=1; i<n; i++){
int x,y,z;
scanf("%d%d%d",&x,&y,&z);
val[i][0] = x;
val[i][1] = y;
val[i][2] = z;
add(x,y,z);
add(y,x,z);
}
memset(tree,0,sizeof(tree));
dfs1(1,1,1);

fn = 0;
dfs2(1,1);

for(i=1; i<n; i++){
if(deq[val[i][0]] > deq[val[i][1]]){
swap(val[i][0],val[i][1]);
}
updata(w[val[i][1]],val[i][2],1,fn,1);
}
char s[15];
while(1)
{
scanf("%s",s);
if(s[0] == 'D')
break;

if(s[0] == 'C'){
int x,y;
scanf("%d%d",&x,&y);
updata(w[val[x][1]],y,1,fn,1);
}
else {
int x,y;
scanf("%d%d",&x,&y);
printf("%d\n",lca(x,y));
}
}
}
}