SPOJ 375 QTREE series-Query on a tree (tree link division), qtree-query

SPOJ 375 QTREE series-Query on a tree (tree link division), qtree-query

Question address: SPOJ 375
The first line of tree link generation!
It seems to be a very advanced data structure. In fact, it is to convert the side of the tree from the tree structure into a linear structure, so that you can use a data structure such as a line segment tree or a tree array for fast maintenance. So that the time is reduced to n * log (2 * n ).
This topic is maintained by the line segment tree.
The Code is as follows:

#include <iostream>#include <string.h>#include <math.h>#include <queue>#include <algorithm>#include <stdlib.h>#include <map>#include <set>#include <stdio.h>using namespace std;#define LL long long#define pi acos(-1.0)//#pragma comment(linker, "/STACK:1024000000")const int mod=1e9+7;const int INF=0x3f3f3f3f;const double eqs=1e-3;const int MAXN=10000+10;#define root 1, n, 1#define lson l, mid, rt<<1#define rson mid+1, r, rt<<1|1int Max[MAXN<<2], head[MAXN], cnt, n;int siz[MAXN], dep[MAXN], w[MAXN], top[MAXN], son[MAXN], fa[MAXN], tot;struct node{        int u, v, w, next;}edge[MAXN<<1];void add(int u, int v, int w){        edge[cnt].u=u;        edge[cnt].v=v;        edge[cnt].w=w;        edge[cnt].next=head[u];        head[u]=cnt++;}void init(){        memset(head,-1,sizeof(head));        cnt=0;        memset(dep,0,sizeof(dep));        memset(son,0,sizeof(son));        memset(Max,0,sizeof(Max));        tot=0;}void dfs1(int u, int p){        siz[u]=1;        for(int i=head[u];i!=-1;i=edge[i].next){                int v=edge[i].v;                if(v==p) continue ;                dep[v]=dep[u]+1;                dfs1(v,u);                fa[v]=u;                if(siz[v]>siz[son[u]]) son[u]=v;                siz[u]+=siz[v];        }}void dfs2(int u, int tp){        w[u]=++tot; top[u]=tp;        if(son[u]) dfs2(son[u],top[u]);        for(int i=head[u];i!=-1;i=edge[i].next){                int v=edge[i].v;                if(v!=son[u]&&v!=fa[u])                        dfs2(v,v);        }}struct Line_Tree{        void PushUp(int rt)        {                Max[rt]=max(Max[rt<<1],Max[rt<<1|1]);        }        void Update(int p, int x, int l, int r, int rt)        {                if(l==r){                        Max[rt]=x;                        return ;                }                int mid=l+r>>1;                if(p<=mid) Update(p,x,lson);                else Update(p,x,rson);                PushUp(rt);        }        int Query(int ll, int rr, int l, int r, int rt)        {                if(ll<=l&&rr>=r){                        return Max[rt];                }                int mid=l+r>>1, ans=0;                if(ll<=mid) ans=max(Query(ll,rr,lson),ans);                if(rr>mid) ans=max(ans,Query(ll,rr,rson));                return ans;        }}lt;int Query(int u, int v){        int f1=top[u], f2=top[v], ans=0;        while(f1!=f2){                if(dep[f1]<dep[f2]){                        swap(u,v);                        swap(f1,f2);                }                ans=max(ans,lt.Query(w[f1],w[u],root));                u=fa[f1];f1=top[u];        }        if(u==v) return ans;        if(dep[u]<dep[v]) swap(u,v);        return max(ans,lt.Query(w[son[v]],w[u],root));}int main(){        int m, q, i, u, v, T, x, c;        char s[10];        scanf("%d",&T);        while(T--){                scanf("%d",&n);                init();                for(i=1;i<n;i++){                        scanf("%d%d%d",&u,&v,&c);                        add(u,v,c);                        add(v,u,c);                }                dfs1(1,-1);                dfs2(1,1);                for(i=0;i<cnt;i+=2){                        u=edge[i].u;                        v=edge[i].v;                        if(dep[u]<dep[v]) swap(u,v);                        lt.Update(w[u],edge[i].w,root);                }                while(scanf("%s",s)!=EOF&&s[0]!='D'){                        if(s[0]=='C'){                                scanf("%d%d",&x,&c);                                u=edge[x-1<<1].u;                                v=edge[x-1<<1].v;                                if(dep[u]<dep[v]) swap(u,v);                                lt.Update(w[u],c,root);                        }                        else{                                scanf("%d%d",&u,&v);                                printf("%d\n",Query(u,v));                        }                }        }        return 0;}