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Tarjan_gd_q.cpp
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Tarjan_gd_q.cpp
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#include <cstdio>
#include <cstring>
#include <algorithm>
#include <iostream>
#include <vector>
#include <map>
using namespace std;
const int MAXN=10010,MAXM=100010;
//点的下标切记转换成由1~n
struct Edge{
int to,next;
bool cut; //是否为桥的标记*******
}edge[MAXM]; //边数组
/* 遍历点u的临接边
for(int i=head[u];i!=-1;i=edge[i].next)
{ edge[i] } //edge[i]即为边
*/
int head[MAXN],tot;
int Low[MAXN],DFN[MAXN],Stack[MAXN];
int Index,top;
bool Instack[MAXN];
bool cut[MAXN]; //是否为割点的标记*********
int add_block[MAXN]; //删除一个点后增加的连通块
int bridge; //记录桥的个数*******
void init(){ //加边前先初始化
memset(DFN,0,sizeof(DFN));
memset(Instack,false,sizeof(Instack));
memset(add_block,0,sizeof(add_block));
memset(cut,false,sizeof(cut));
memset(head,-1,sizeof(head));
tot=Index=top=bridge=0;
}
void add_edge(int u,int v){ //添加无向边,只需调用一次!!!!!!!!!
edge[tot].to=v; edge[tot].next=head[u] ; edge[tot].cut=false;
head[u]=tot++;
edge[tot].to=u; edge[tot].next=head[v] ; edge[tot].cut=false;
head[v]=tot++;
}
void Tarjan(int u,int pre){
int v;
// cout<<u<<" "<<pre<<endl;
Low[u]=DFN[u]=++Index;
Stack[top++]=u;
Instack[u]=true;
int son=0;
for(int i=head[u];i!=-1;i=edge[i].next){
v=edge[i].to;
if(v==pre)continue;
if(!DFN[v]){ //如果没有访问过v
son++;
Tarjan(v,u);
if(Low[u]>Low[v])Low[u]=Low[v];
//判断无向边(u,v)是否是桥
if(Low[v]>DFN[u]){
bridge++;
edge[i].cut=true;
edge[i^1].cut=true;
}
//判断u是否为割点
if(u!=pre&&Low[v]>=DFN[u]){
cut[u]=true;
add_block[u]++;
}
}
else if(Low[u]>DFN[v])
Low[u]=DFN[v];
}
if(u==pre&&son>1)cut[u]=true;
if(u==pre)add_block[u]=son-1;
Instack[u]=false;
top--;
}
void solve(int N){ // 寻找割顶和桥,N为题目中结点数
for(int i=1;i<=N;i++)
if(!DFN[i])Tarjan(i,i); //对于每一个连通分量都调用一次
}