[HNOI2006]超级英雄Hero

这题一看就应该知道是二分图匹配……

我记得有个类似的题有一个并查集的解法，但是我找不到了……

 1 var i,n,m:longint;

 2     p:array[0..1500] of longint;

 3     v:array[0..1500] of boolean;

 4     a:array[0..1500,1..2] of longint;

 5 function find(x:longint):boolean;

 6  var i,y:longint;

 7  begin

 8  for i:=1 to 2 do

 9   begin

10   y:=a[x,i];

11   if v[y] then continue;

12   v[y]:=true;

13   if (p[y]=0) or (find(p[y])) then

14    begin

15    p[y]:=x;

16    exit(true);

17    end;

18   end;

19  exit(false);

20  end;

21 procedure main;

22  begin

23  readln(n,m);

24  for i:=1 to m do begin readln(a[i,1],a[i,2]);inc(a[i,1]);inc(a[i,2]);end;

25  for i:=1 to m do

26   begin

27   fillchar(v,sizeof(v),false);

28   if not(find(i)) then begin writeln(i-1);halt;end;

29   end;

30  writeln(m);

31  end;

32 begin

33  main;

34 end.        

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