树链剖分模板

  1 #include <iostream>
  2 #include <cstdio>
  3 #include <cstdlib>
  4 #include <cmath>
  5 #include <algorithm>
  6 #include <cstring>
  7 #include <stack>
  8 #include <cctype>
  9 #include <queue>
 10 #include <string>
 11 #include <vector>
 12 #include <set>
 13 #include <map>
 14 #include <climits>
 15 #define lson rt<<1,l,mid
 16 #define rson rt<<1|1,mid+1,r
 17 #define fi first
 18 #define se second
 19 #define ping(x,y) ((x-y)*(x-y))
 20 #define mst(x,y) memset(x,y,sizeof(x))
 21 #define mcp(x,y) memcpy(x,y,sizeof(y))
 22 using namespace std;
 23 #define gamma 0.5772156649015328606065120
 24 #define MOD 1000000007
 25 #define inf 0x3f3f3f3f
 26 #define N 10050
 27 #define maxn 30010
 28 typedef pair<int,int> PII;
 29 typedef long long LL;
 30 LL read(){
 31     LL x=0,f=1;char ch=getchar();
 32     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
 33     while(ch>=‘0‘&&ch<=‘9‘){x=(x<<3)+(x<<1)+ch-‘0‘;ch=getchar();}
 34     return x*f;
 35 }
 36 int n,m,k,head[N],hcnt,rt;
 37 char str[11];
 38 struct Node{
 39     int to,nxt,v;
 40 }node[maxn];
 41 struct Edge{
 42     int x,y,v;
 43 }edge[maxn];
 44 int seg[N<<2];
 45 
 46 int siz[N];  ///当前节点保存的儿子数
 47 int top[N];  ///当前节点所在链的顶端节点
 48 int son[N];  ///保存重儿子
 49 int dep[N];  ///当前节点深度
 50 int fa[N];   ///当前节点的父亲
 51 int id[N];   ///用来保存树中每个节点剖分后的新编号
 52 int posi[N]; ///在线段树中的位置
 53 int tid,pos;
 54 
 55 ///树链剖分
 56 void dfs1(int u,int f,int deep){ ///找重边
 57     dep[u]=deep;
 58     fa[u]=f;
 59     siz[u]=1;
 60     for(int i=head[u];~i;i=node[i].nxt){
 61         int e=node[i].to;
 62         if(e==f)continue;
 63         dfs1(e,u,deep+1);
 64         siz[u]+=siz[e];
 65         if(!son[u]||siz[son[u]]<siz[e])
 66             son[u]=e;
 67     }
 68 }
 69 void dfs2(int u,int tp){   ///连重边成重链
 70     top[u]=tp;
 71     id[u]=++tid;
 72     posi[id[u]]=u;
 73     if(!son[u])return;
 74     dfs2(son[u],tp);
 75     for(int i=head[u];~i;i=node[i].nxt){
 76         int e=node[i].to;
 77         if(e!=son[u]&&e!=fa[u])
 78             dfs2(e,e);
 79     }
 80 }
 81 
 82 ///线段树
 83 void build(int rt,int l,int r){
 84     seg[rt]=-inf;
 85     if(l==r) return;
 86     int mid=l+r>>1;
 87     build(lson); build(rson);
 88     seg[rt]=max(seg[rt<<1],seg[rt<<1|1]);
 89 }
 90 
 91 void add(int rt,int l,int r,int v){
 92     if(l==r){
 93         seg[rt]=v;
 94         return;
 95     }
 96     int mid=l+r>>1;
 97     if(pos<=mid)add(lson,v);
 98     else add(rson,v);
 99     seg[rt]=max(seg[rt<<1],seg[rt<<1|1]);
100 }
101 int query(int rt,int l,int r,int L,int R){
102     if(L<=l&&r<=R){return seg[rt];}
103     int mid=l+r>>1;
104     int temp=INT_MIN;
105     if(L<=mid)temp=max(temp,query(lson,L,R));
106     if(R>mid) temp=max(temp,query(rson,L,R));
107     return temp;
108 }
109 
110 void ini(){
111     mst(head,-1);hcnt=tid=0;mst(seg,0);
112     mst(son,0);mst(siz,0);
113 }
114 void add(int x,int y,int v){
115     node[hcnt].to=y,node[hcnt].nxt=head[x],node[hcnt].v=v,head[x]=hcnt++;
116     node[hcnt].to=x,node[hcnt].nxt=head[y],node[hcnt].v=v,head[y]=hcnt++;
117 }
118 int lca(int x,int y){
119     int ans=-inf;
120     while(top[x]!=top[y]){
121         if(dep[top[x]]<dep[top[y]])swap(x,y);
122         ans=max(ans,query(1,1,n,id[top[x]],id[x]));
123         x=fa[top[x]];
124     }
125     if(dep[x]>dep[y])swap(x,y);
126     if(x!=y)ans=max(ans,query(1,1,n,id[x]+1,id[y]));
127     return ans;
128 }
129 int main(){
130     //freopen("in.txt","r",stdin);
131     int i,j,group,x,y,v,Case=0;
132     group=read();
133     while(group--){
134         ini();
135         n=read();
136         for(i=1;i<n;++i){
137             scanf("%d%d%d",&x,&y,&v);
138             edge[i].x=x,edge[i].y=y,edge[i].v=v;
139             add(x,y,v);
140         }
141         dfs1(1,1,1);
142         dfs2(1,1);
143         build(1,1,n);
144         for(i=1;i<n;i++){
145             if(dep[edge[i].x]<dep[edge[i].y])
146                 swap(edge[i].x,edge[i].y);
147             pos=id[edge[i].x];
148             add(1,1,n,edge[i].v);
149         }
150         while(scanf("%s",str)!=EOF){
151             if(str[0]==‘D‘)break;
152             x=read();y=read();
153             if(str[0]==‘Q‘){
154                 printf("%d\n",lca(x,y));
155             }
156             else{
157                 pos=id[edge[x].x];
158                 add(1,1,n,y);
159             }
160         }
161         printf("\n");
162     }
163     return 0;
164 }