dfs一遍得到每一个节点的dfs序,对于要插入的节点x分两种情况考虑:
1,假设x能够在集合中的某些点之间,找到左边和右边距离x近期的两个点,即DFS序小于x的DFS序最大点,和大于x的DFS序最小的点......
2.假设x在集合中的点某一側,则找距离x的dfs序最小和最大的点
将x插入这个集合最少要走的距离为 dist[x]-dist[LCA(left,x)]-dist[LCA(right,x)]+dist[LCA(left,right)]
删除同理
Annoying problem
Time Limit: 16000/8000 MS (Java/Others) Memory Limit: 65536/65536 K (Java/Others)
Total Submission(s): 334 Accepted Submission(s): 95
Problem Description
Coco has a tree, whose nodes are conveniently labeled by 1,2,…,n, which has n-1 edge。each edge has a weight. An existing set S is initially empty.
Now there are two kinds of operation:
1 x: If the node x is not in the set S, add node x to the set S
2 x: If the node x is in the set S,delete node x from the set S
Now there is a annoying problem: In order to select a set of edges from tree after each operation which makes any two nodes in set S connected. What is the minimum of the sum of the selected edges’ weight ?
Input
one integer number T is described in the first line represents the group number of testcases.( T<=10 )
For each test:
The first line has 2 integer number n,q(0<n,q<=100000) describe the number of nodes and the number of operations.
The following n-1 lines each line has 3 integer number u,v,w describe that between node u and node v has an edge weight w.(1<=u,v<=n,1<=w<=100)
The following q lines each line has 2 integer number x,y describe one operation.(x=1 or 2,1<=y<=n)
Output
Each testcase outputs a line of "Case #x:" , x starts from 1.
The next q line represents the answer to each operation.
Sample Input
1 6 5 1 2 2 1 5 2 5 6 2 2 4 2 2 3 2 1 5 1 3 1 4 1 2 2 5
Sample Output
Case #1: 0 6 8 8 4
Author
FZUACM
Source
2015 Multi-University Training Contest 1
/* *********************************************** Author :CKboss Created Time :2015年07月21日 星期二 21时06分11秒 File Name :HDOJ5296.cpp ************************************************ */ #include <iostream> #include <cstdio> #include <cstring> #include <algorithm> #include <string> #include <cmath> #include <cstdlib> #include <vector> #include <queue> #include <set> #include <map> using namespace std; typedef long long int LL; const int maxn=120100; const int INF=0x3f3f3f3f; struct Edge { int to,next,cost; }edge[maxn*2]; int Adj[maxn],Size; void init() { memset(Adj,-1,sizeof(Adj)); Size=0; } void Add_Edge(int u,int v,int c) { edge[Size].to=v; edge[Size].cost=c; edge[Size].next=Adj[u]; Adj[u]=Size++; } int n,q; int dist[maxn],ti[maxn],cnt; void dfs(int len,int u,int fa) { dist[u]=len; ti[u]=cnt; for(int i=Adj[u];~i;i=edge[i].next) { int to=edge[i].to; int cost=edge[i].cost; if(to==fa) continue; cnt++; dfs(len+cost,to,u); } } /********************** LCA **********************************/ const int DEG=20; int fa[maxn][DEG]; int deg[maxn]; void BFS(int root) { queue<int> q; memset(deg,0,sizeof(deg)); memset(fa,0,sizeof(fa)); deg[root]=0; fa[root][0]=root; q.push(root); while(!q.empty()) { int u=q.front(); q.pop(); for(int i=1;i<DEG;i++) { fa[u][i]=fa[fa[u][i-1]][i-1]; } for(int i=Adj[u];~i;i=edge[i].next) { int v=edge[i].to; if(v==fa[u][0]) continue; deg[v]=deg[u]+1; fa[v][0]=u; q.push(v); } } } int LCA(int u,int v) { if(deg[u]>deg[v]) swap(u,v); int hu=deg[u],hv=deg[v]; int tu=u,tv=v; for(int det=hv-hu,i=0;det;i++,det=det/2) { if(det&1) tv=fa[tv][i]; } if(tu==tv) return tu; for(int i=DEG-1;i>=0;i--) { if(fa[tu][i]==fa[tv][i]) continue; tu=fa[tu][i]; tv=fa[tv][i]; } return fa[tu][0]; } struct Node { int val,cnt; bool operator<(const Node& nd) const { return cnt<nd.cnt; } bool operator==(const Node& nd) const { return val==nd.val; } bool operator!=(const Node& nd) const { return val!=nd.val; } }; set<Node> st; int CL(int flag,Node ND) { if(flag==0) st.erase(ND); set<Node>::iterator it1,it2; int x=ND.val; it2=st.upper_bound(ND); it1=it2; it1--; /// check if in mid if(it1->val!=0&&it2->val!=n+10) /// in mid { int left=it1->val; int right=it2->val; if(flag) st.insert(ND); return dist[x]-dist[LCA(x,left)]-dist[LCA(x,right)]+dist[LCA(left,right)]; } else // in side { if(it2->val==n+10) /// all in left { it2=st.begin(); it2++; int left=it2->val; int right=it1->val; if(flag) st.insert(ND); return dist[x]-dist[LCA(x,left)]-dist[LCA(x,right)]+dist[LCA(left,right)]; } else if(it1->val==0) /// all in right { int left=it2->val; it1=st.end(); it1--; it1--; int right=it1->val; if(flag) st.insert(ND); return dist[x]-dist[LCA(x,left)]-dist[LCA(x,right)]+dist[LCA(left,right)]; } } } /// return change val of solve int solve(int kind,int x) { Node ND = (Node){x,ti[x]}; /// if in mid find nearst point set<Node>::iterator it1,it2; if(kind==1) // add { if(st.count(ND)==1) return 0; if(st.size()==2) { st.insert(ND); return 0; } else if(st.size()==3) { it1=st.begin(); it1++; int v=it1->val; st.insert(ND); return dist[x]+dist[v]-2*dist[LCA(v,x)]; } else { return CL(1,ND); } } else if(kind==2) // remove { if(st.count(ND)==0) return 0; if(st.size()==3) { st.erase(ND); return 0; } else if(st.size()==4) { it1=st.begin(); it1++; int v=it1->val; it1++; int u=it1->val; st.erase(ND); return dist[u]+dist[v]-2*dist[LCA(u,v)]; } else { return CL(0,ND); } } } int main() { //freopen("in.txt","r",stdin); //freopen("out.txt","w",stdout); int T_T,cas=1; scanf("%d",&T_T); while(T_T--) { scanf("%d%d",&n,&q); init(); for(int i=0,u,v,c;i<n-1;i++) { scanf("%d%d%d",&u,&v,&c); Add_Edge(u,v,c); Add_Edge(v,u,c); } cnt=1; st.clear(); st.insert((Node){0,-INF}); st.insert((Node){n+10,INF}); dfs(0,1,1); BFS(1); int all=0; printf("Case #%d:\n",cas++); while(q--) { int k,x; scanf("%d%d",&k,&x); if(k==1) all+=solve(k,x); else if(k==2) all-=solve(k,x); printf("%d\n",all); } } return 0; }