POJ3694 Network Cutting Edge +lca

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Test instructions

A connected graph of n(1≤ n ≤100,000) points and m(n -1≤ m ≤200,000) is given.

have q (1≤ Q ≤1,000) Ask each query to add an edge (accumulate)

The number of bridges remaining after each additional edge is output

Exercises

10W Point Plus 1000 queries every time you ask for a tarjin algorithm, you'll definitely time out.

Consider the essence of a-B at a time of adding one edge:

All cut edges in the path from A to B will disappear

So how do you record this path?

Build a tree by the edge of the Tarjan algorithm during recursion

Then each query starts from a B until the edges of their nearest public ancestor disappear.

Code:

#include <iostream> #include <cstdio> #include <cstring> #include <vector> #define MAXN 100050using namespace std;struct node{int to,next;} Edge[maxn*4];int head[maxn];int s;int dfn[maxn],low[maxn],num;int level[maxn],fa[maxn];int flag[maxn];int n,ans;void    Init () {memset (head,-1,sizeof (head));    memset (dfn,0,sizeof (DFN));    memset (flag,0,sizeof (flag));    s=ans=num=0;    level[0]=0; for (int i=1;i<=n;i++) fa[i]=i;}    void Addedge (int a,int b) {Edge[s]={b,head[a]}; head[a]=s++;}        void LCA (int a,int b) {while (Level[b]>level[a]) {if (Flag[b]) ans--, flag[b]=0;    B=FA[B];        } while (Level[a]>level[b]) {if (Flag[a]) ans--, flag[a]=0;    A=fa[a];        } while (a!=b) {if (Flag[a]) ans--, flag[a]=0;        if (Flag[b]) ans--, flag[b]=0;    A=FA[A],B=FA[B];    }}void Tarjan (int u,int pre) {dfn[u]=low[u]=++num;              level[u]=level[pre]+1; Achievements for (inT i=head[u];i!=-1;i=edge[i].next) {int v=edge[i].to;            if (!dfn[v]) {fa[v]=u;            Tarjan (V,u);            Low[u]=min (Low[u],low[v]);        if (Dfn[u]<low[v])//Mark cutting edge flag[v]=1,ans++;    } if (V!=pre) low[u]=min (Low[u],dfn[v]);    }}int Main () {int m,a,b;    int case=1;        while (scanf ("%d%d", &n,&m) && (n+m)) {init ();            while (m--) {scanf ("%d%d", &a,&b);            Addedge (A, b);        Addedge (B,a);        } Tarjan (1,0);        scanf ("%d", &m);        printf ("Case%d:\n", case++);            while (m--) {scanf ("%d%d", &a,&b);            if (ans!=0) LCA (A, b);        printf ("%d\n", ans);    } printf ("\ n"); } return 0;}

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POJ3694 Network Cutting Edge +lca