spoj qtree Query on a tree 【线段树+树链剖分】

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>#include <vector>#include <queue>#include <stack>#include <set>#include <map>#include <string>#include <cmath>#include <stdlib.h>#include <time.h>using namespace std;typedef vector<int> VI;typedef unsigned long long ull;typedef long long ll;typedef double db;const ll mod=1000000007;const int N=10000+10;const int inf=0x7fffffff;struct edge{    int a,b,w;}g[2*N];vector<int>v[N];int fa[N],dep[N],sz[N],son[N],w[N],vis[N],top[N],tot;void dfs1(int x,int f){    int y,mx=-1;     vis[x]=1;     fa[x]=f;     sz[x]=1;     dep[x]=dep[f]+1;     for(int i=0;i<v[x].size();i++)     {         y=v[x][i];         if(vis[y]==1) continue;         dfs1(y,x);         sz[x]+=sz[y];         if(sz[y]>mx){mx=sz[y];son[x]=y;}     }}void dfs2(int x,int tp){    top[x]=tp;    if(son[x]!=0)    {        w[x]=tot++;        dfs2(son[x],tp);    }    else    {        w[x]=tot++;        return ;    }    int y;    for(int i=0;i<v[x].size();i++)    {        y=v[x][i];        if(y!=son[x]&&y!=fa[x])            dfs2(y,y);    }}struct Tree{    int l,r,mx;}tree[4*N];void build(int o,int l,int r){    tree[o].l=l;    tree[o].r=r;    tree[o].mx=0;    if(l!=r)    {        int mid=(l+r)/2;        build(o*2,l,mid);        build(o*2+1,mid+1,r);    }}void update(int o,int l,int r,int val){    if(l<=tree[o].l&&tree[o].r<=r)    {        tree[o].mx=val;    }    else    {        int mid=(tree[o].l+tree[o].r)/2;        if(l<=mid)  update(o*2,l,r,val);        if(r>mid) update(o*2+1,l,r,val);        tree[o].mx=max(tree[o*2].mx,tree[o*2+1].mx);    }}int query(int o,int l,int r){    if(l<=tree[o].l&&tree[o].r<=r)    {        return tree[o].mx;    }    else    {        int ans=0;        int mid=(tree[o].l+tree[o].r)/2;        if(l<=mid) ans=max(ans,query(o*2,l,r));        if(r>mid) ans=max(ans,query(o*2+1,l,r));        return ans;    }}int Find(int x,int y){    int f1=top[x],f2=top[y];    int tmp=0;    while(f1!=f2)    {        if(dep[f1]<dep[f2])        {            swap(f1,f2);            swap(x,y);        }        tmp=max(tmp,query(1,w[f1],w[x]));        x=fa[f1];        f1=top[x];    }    if(x==y) return tmp;    if(dep[x]>dep[y]) swap(x,y);    return max(tmp,query(1,w[son[x]],w[y]));}int main(){    //freopen("in.txt","r",stdin);    //freopen("out.txt","w",stdout);    int _,n,a,b,c;    char s[100];    scanf("%d",&_);    while(_--)    {        scanf("%d",&n);        for(int i=1;i<=n;i++)            v[i].clear();        for(int i=0;i<n-1;i++)        {            scanf("%d%d%d",&a,&b,&c);            g[i].a=a;g[i].b=b;            g[i].w=c;            v[a].push_back(b);            v[b].push_back(a);        }        memset(vis,0,sizeof(vis));        memset(son,0,sizeof(son));        tot=1;        dep[0]=0;        dfs1(1,0);        dfs2(1,1);        build(1,1,tot-1);        for(int i=0;i<n-1;i++)        {            a=g[i].a;b=g[i].b;            if(dep[a]>dep[b])                 swap(g[i].a,g[i].b);            update(1,w[g[i].b],w[g[i].b],g[i].w);        }        while(~scanf("%s",s))        {            if(s[0]=='D') break;            scanf("%d%d",&a,&b);            if(s[0]=='C')                update(1,w[g[a-1].b],w[g[a-1].b],b);            else                printf("%d\n",Find(a,b));        }    }    return 0;}