tarjan帮我来找桥

来源：互联网发布：ug五轴编程工资多少钱编辑：程序博客网时间：2024/05/01 12:48

http://acm.hust.edu.cn/vjudge/contest/129458#problem/B
判断图中各个联通分量是不是只有中间一条桥，两边都是完全图

这里写图片描述

#include <cstdio>#include <cstring>#include <iostream>#include <vector>#define maxn 110using namespace std;vector<int>vc[maxn];int low[maxn];int val[maxn];int T = 0,ans = 0;int X,U;bool vis[maxn];   //区分不同的连通块。当前点在之前的块中找过就不在重复找，ca之间初始化int no,edge,QQ;   //QQ表示该连通块多少个点void dfs(int x,int fa){  val[x] = T;  vis[x] = true;  QQ++;  low[x] = T++;  for(int i = 0; i < vc[x].size();i++){    int u = vc[x][i];    if(u == fa)      continue;    if(val[u] == -1){      dfs(u,x);      if(low[u] > val[x]){         ans++;         X = x;   //桥的两边两个点分别是X和U         U = u;      }      low[x] = min(low[x],low[u]);    }    else      low[x] = min(low[x],val[u]);  }}void init(){  scanf("%d%d",&no,&edge);  for(int i = 0 ; i < edge ;i++){    int u,v;    scanf("%d%d",&u,&v);    vc[u].push_back(v);    vc[v].push_back(u);  }}int sov(int tmp,int cnt,int s){  for(int i = 0 ; i < vc[tmp].size();i++){    cnt++;    if( vc[vc[tmp][i]].size() != (QQ/2-1) &&vc[tmp][i]!= s){      return -1;    }  }  return cnt;}void inital(){  QQ = 0;  ans = 0;  T = 0;  memset(val,-1,sizeof(val));  memset(low,-1,sizeof(low));}int main(){  int Ca;  cin >> Ca;  int ca = 1;  while(Ca--){    printf("Case #%d: ",ca++);    init();    memset(vis,false,sizeof(vis));    int ANS = 0;    for(int i = 1; i <= no ;i++){      if(vis[i] == true)        continue;      inital();      dfs(i,-1);      if(ans == 1){        int c1 = sov(X,0,U),j;        if(c1 == -1)          continue;        int c2 = sov(U,0,X);        if(c2 == -1)          continue;        if(c1 == c2)          ANS++;      }          if(ans == 3 && QQ == 4&&vc[X].size() != 3 && vc[U].size() != 3)//四个点一条串串也是可以的        ANS++;    }  cout <<ANS<<endl;  for(int i = 1 ; i <= no ;i++)    vc[i].clear();  }}

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