HDU 5692 (DFS序+线段树)

DFS获得从0到每一个顶点的距离，同时获得L和R数组。两数组为遍历时从i进入再从i出来的序列。

 #pragma comment(linker, "/STACK:1024000000,1024000000")
 #include <iostream>
 #include <cstdio>
 #include <algorithm>
 #include <cstring>
 #include <vector>
 using namespace std;
 const int maxn = 1e5+;

 typedef long long ll;
 const ll inf = 0x3f3f3f3f3f3f3f3f;
 int n,m;
 vector<int> g[maxn];
 ll w[maxn];
 int index = ;
 int L[maxn],R[maxn];
 int vis[maxn];
 ll d[maxn];
 struct node
 {
     ll maxx;
     ll lazy;
 };
 node T[maxn*];
 void dfs(int x,int New)
 {
     L[x] = index;
     for(int i=;i<g[x].size();i++)
     {
         int v = g[x][i];
         if(!vis[v])
         {
             vis[v] = ;
            index++;
            d[index] = d[New]+w[v];
            dfs(v,index);
         }
     }
     R[x] = index;
 }
 void build(int q,int l,int r)
 {
     if(l==r)
     {
         T[q].maxx = d[l];
         T[q].lazy = ;
         return;
     }
     int mid = (l+r)/;
     build(q*,l,mid);
     build(q*+,mid+,r);
     T[q].lazy = ;
     T[q].maxx = max(T[q*].maxx,T[q*+].maxx);
 }
 void ins(int q,int l,int r,int ql,int qr,ll tt)
 {
     if(ql<=l&&r<=qr)
     {
         T[q].maxx += tt;
         T[q].lazy += tt;
         return;
     }
     if(T[q].lazy)
     {
         T[q*].maxx += T[q].lazy;
         T[q*].lazy += T[q].lazy;
         T[q*+].maxx += T[q].lazy;
         T[q*+].lazy += T[q].lazy;
         T[q].lazy = ;
     }
     int mid = (l+r)/;
     if(ql<=mid) ins(q*,l,mid,ql,qr,tt);
     if(mid+<=qr) ins(q*+,mid+,r,ql,qr,tt);
     T[q].maxx = max(T[q*].maxx,T[q*+].maxx);
     return;
 }
 ll query(int q,int l,int r,int ql,int qr)
 {
     if(ql<=l&&qr>=r)
     {
         return T[q].maxx;
     }
     if(T[q].lazy)
     {
         T[q*].maxx += T[q].lazy;
         T[q*].lazy += T[q].lazy;
         T[q*+].maxx += T[q].lazy;
         T[q*+].lazy += T[q].lazy;
         T[q].lazy = ;
     }
     ll maxx = -inf;   //坑点
     int mid = (l+r)/;
     if(ql<=mid) maxx = max(maxx,query(q*,l,mid,ql,qr));
     if(mid+<=qr) maxx = max(maxx,query(q*+,mid+,r,ql,qr));
     return maxx;
 }
 int main()
 {
     int T,kase = ;cin>>T;
     while(T--)
     {
         scanf("%d %d",&n,&m);
         for(int i=;i<=n;i++) g[i].clear();
         int xx,xy;
         for(int i=;i<=n-;i++)
         {
             scanf("%d %d",&xx,&xy);
             g[xx].push_back(xy);
             g[xy].push_back(xx);
         }
         for(int i=;i<n;i++) scanf("%I64d",&w[i]);
         index = ;
         memset(d,,sizeof(d));
         memset(vis,,sizeof(vis));
         memset(L,,sizeof(L));
         memset(R,,sizeof(R));
         d[] = w[];
         vis[] = ;
         dfs(,);
         build(,,n);
         printf("Case #%d:\n",++kase);
         int x,y;
         ll ttt;
         for(int i=;i<=m;i++)
         {
             scanf("%d %d",&x,&y);
             if(x==)
             {
                 printf("%I64d\n",query(,,n,L[y],R[y]));
             }
             else
             {
                 scanf("%I64d",&ttt);
                 ll tt = ttt-w[y];
                 ins(,,n,L[y],R[y],tt);
                 w[y] = ttt;  //坑点
             }
         }
     }
     return ;
 }