tarjan求強連通分量

dfn記錄的是初次訪問的時間

low記錄的是最小的訪問時間

view記錄的是訪問過幾次，0次可以訪問，1次時更新low值，2次表示已出棧，不再訪問

 

 

2話不說，貼代碼，應該只比HYC小牛快上30%左右......很失落.......

 

 

program tarjan; var i,j,k,x,y,time,n,p,q,ans:longint; dfn,low,view,head,next,list,e,map:array[0..100]of longint; function min(a,b:longint):longint; begin if a<b then exit(a) else exit(b); end; procedure dfs(x:longint); var i,j:longint; begin view[x]:=1; inc(list[0]); list[list[0]]:=x; inc(time); dfn[x]:=time; low[x]:=time; j:=head[x]; while j<>0 do begin if view[e[j]]=0 then dfs(e[j]); if view[e[j]]=1 then low[x]:=min(low[x],low[e[j]]); j:=next[j]; end; if low[x]=dfn[x] then begin inc(ans); while list[list[0]]<>x do begin map[list[list[0]]]:=ans; view[list[list[0]]]:=2; dec(list[0]); end; map[list[list[0]]]:=ans; view[list[list[0]]]:=2; dec(list[0]); end; end; begin assign(input,'tarjan.in'); reset(input); assign(output,'tarjan.out'); rewrite(output); read(n,k); for i:=1 to k do begin read(x,y); e[i]:=y; if head[x]=0 then head[x]:=i else begin p:=head[x]; while p<>0 do begin q:=p; p:=next[q]; end; next[q]:=i; end; end; dfs(1); writeln(ans); end.