[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.
