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;

begin
while not seekeof do
begin
   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.