SPOJ QTREE Query on a tree

  1 #include <bits/stdc++.h>
  2 using namespace std;
  3 const int maxn = 10100;
  4 struct arc{
  5     int to,next;
  6     arc(int x = 0,int y = -1){
  7         to = x;
  8         next = y;
  9     }
 10 }e[30000];
 11 struct node{
 12     int lt,rt,val;
 13 }tree[maxn<<2];
 14 int head[maxn],fa[maxn],dep[maxn],son[maxn],tot;
 15 int siz[maxn],top[maxn],tid[maxn],label;
 16 void add(int u,int v){
 17     e[tot] = arc(v,head[u]);
 18     head[u] = tot++;
 19 }
 20 void Find_heavy_edge(int u,int father,int depth){
 21     siz[u] = 1;
 22     dep[u] = depth;
 23     fa[u] = father;
 24     son[u] = -1;
 25     for(int i = head[u]; ~i; i = e[i].next){
 26         if(e[i].to == father) continue;
 27         Find_heavy_edge(e[i].to,u,depth + 1);
 28         siz[u] += siz[e[i].to];
 29         if(son[u] == -1 || siz[e[i].to] > siz[son[u]])
 30             son[u] = e[i].to;
 31     }
 32 }
 33 void connect_heavy_edge(int u,int ancestor){
 34     tid[u] = label++;
 35     top[u] = ancestor;
 36     for(int i = head[u]; ~i; i = e[i].next){
 37         if(e[i].to == fa[u]) continue;
 38         if(e[i].to == son[u]) connect_heavy_edge(e[i].to,ancestor);
 39         else connect_heavy_edge(e[i].to,e[i].to);
 40     }
 41 }
 42 inline void pushup(int v){
 43     tree[v].val = max(tree[v<<1].val,tree[v<<1|1].val);
 44 }
 45 void build(int lt,int rt,int v){
 46     tree[v].lt = lt;
 47     tree[v].rt = rt;
 48     tree[v].val = 0;
 49     if(lt == rt) return;
 50     int mid = (lt + rt)>>1;
 51     build(lt,mid,v<<1);
 52     build(mid+1,rt,v<<1|1);
 53 }
 54 void update(int pos,int val,int v){
 55     if(tree[v].lt == tree[v].rt){
 56         tree[v].val = val;
 57         return;
 58     }
 59     if(pos <= tree[v<<1].rt) update(pos,val,v<<1);
 60     if(pos >= tree[v<<1|1].lt) update(pos,val,v<<1|1);
 61     pushup(v);
 62 }
 63 int query(int lt,int rt,int v){
 64     int ret = 0;
 65     if(lt <= tree[v].lt && rt >= tree[v].rt) return tree[v].val;
 66     if(lt <= tree[v<<1].rt) ret = query(lt,rt,v<<1);
 67     if(rt >= tree[v<<1|1].lt) ret = max(ret,query(lt,rt,v<<1|1));
 68     return ret;
 69 }
 70 int Find(int u,int v){
 71     int f1 = top[u],f2 = top[v],tmp = 0;
 72     while(f1 != f2){
 73         if(dep[f1] < dep[f2]){
 74             swap(f1,f2);
 75             swap(u,v);
 76         }
 77         tmp = max(tmp,query(tid[f1],tid[u],1));
 78         u = fa[f1];
 79         f1 = top[u];
 80     }
 81     if(u == v) return tmp;
 82     if(dep[u] > dep[v]) swap(u,v);
 83     return max(tmp,query(tid[son[u]],tid[v],1));
 84 }
 85 int ac[maxn][3];
 86 int main(){
 87     int kase,n,u,v;
 88     char op[10];
 89     scanf("%d",&kase);
 90     while(kase--){
 91         memset(head,-1,sizeof head);
 92         scanf("%d",&n);
 93         for(int i = tot = 0; i < n-1; ++i){
 94             scanf("%d%d%d",&ac[i][0],&ac[i][1],&ac[i][2]);
 95             add(ac[i][0],ac[i][1]);
 96             add(ac[i][1],ac[i][0]);
 97         }
 98         label = 0;
 99         Find_heavy_edge(1,0,0);
100         connect_heavy_edge(1,1);
101         build(0,label-1,1);
102         for(int i = 0; i < n-1; ++i){
103             if(dep[ac[i][0]] > dep[ac[i][1]])
104                 swap(ac[i][0],ac[i][1]);
105             update(tid[ac[i][1]],ac[i][2],1);
106         }
107         while(~scanf("%s",op)){
108             if(op[0] == ‘D‘) break;
109             scanf("%d%d",&u,&v);
110             if(op[0] == ‘Q‘) printf("%d\n",Find(u,v));
111             else update(tid[ac[u-1][1]],v,1);
112         }
113     }
114     return 0;
115 }