POJ 3352(Tarjen中Low的性质）

这题做了半天……结果发现自己缩点错了……

言归正传，这题给了一个无向图G，求添加几条边后双连通……

做了一上午Tarjen不对……Low就是不满足性质（后来发现这是无向图的，要用有向图版本……——用有向图法做无向图……）

终于……做完了（请忽略Stack，我最后索性直接用Low值了……勉强算hash？）

Program P3352;const   maxn=1000;   maxm=1000;var   n,m,i,j,x,y:longint;   b:array[1..maxn,1..maxn] of boolean;   indegree,c,stack,a,low:array[1..maxn] of longint;   size,time:longint;function min(a,b:longint):longint;begin   if a<b then exit(a) else exit(b);end;function max(a,b:longint):longint;begin   if a>b then exit(a) else exit(b);end;procedure swap(a,b:longint);var   p:longint;begin   p:=a;   a:=b;   b:=p;end;procedure tarjan(k,father{,deep}:longint);var   i,j:longint;begin   inc(size);   stack[size]:=k;     //for suo_dian^_^   inc(time);   a[k]:=time;   low[k]:=time; {   low[k]:=deep;   a[k]:=deep;  }   c[k]:=1;   for i:=1 to n do   begin      if (b[i,k]) and (i<>father) and (a[i]<a[k]) then      begin         if c[i]=0 then         begin            tarjan(i,k{,deep+1});            low[k]:=min(low[k],low[i]);         end;         if (c[i]=1) and (i<>father) then         begin            low[k]:=min(low[k],a[i]);         end;      end;   end;   c[k]:=2;end;procedure main;var   i,j,tot:longint;begin   fillchar(stack,sizeof(stack),0);   fillchar(a,sizeof(a),0);   fillchar(low,sizeof(low),0);   fillchar(c,sizeof(c),0);   fillchar(indegree,sizeof(indegree),0);   size:=0;time:=0;   tarjan(1,0{,1});   for i:=1 to n do      for j:=i+1 to n do         if (low[i]<>low[j]) and (b[i,j]) then         begin            inc(indegree[low[i]]);            inc(indegree[low[j]]);         end;   tot:=0;   for i:=1 to n do if indegree[i]=1 then inc(tot);   writeln((tot+1) div 2);end;beginwhile not seekeof dobegin   fillchar(b,sizeof(b),false);   read(n,m);   for i:=1 to m do   begin      read(x,y);      b[x,y]:=true;      b[y,x]:=true;   end;   main;end;end.