I got WA in the 11th data, and I've readen the discussion in the webboard, but them made me even more puzzled. What should I do with the branch which is 0 on earth? And what about when n=q? Would you please help me?
And this is my program, I will be very thankful if you can tell me what's wrong with my program too.
First, I use e and cost to record the nodes and numbers of apples. Then I build up a tree, delete the branch which is on the top and with the fewest apples. When k=n-1-m, the answer comes out.
As follow:
type aas=record
     bef:shortint;
     val:integer;
     nex:array[1..2]of byte;
end;
var i,j,k,t,n,m,a,b,c:integer;
    ans:longint;
    tree:array[1..100]of aas;
    e:array[1..100,1..3]of shortint;
    cost:array[1..100,1..3]of integer;
    num:array[1..100]of shortint;
    mark:array[1..100]of shortint;

procedure find(aa:integer);
var i2:integer;
begin
     for i2:=1 to num[aa] do if mark[e[aa,i2]]=0 then begin
         inc(mark[aa]);
         tree[aa].nex[mark[aa]]:=e[aa,i2];
         tree[e[aa,i2]].bef:=aa;
         tree[e[aa,i2]].val:=cost[aa,i2];
     end;
     for i2:=1 to mark[aa] do find(tree[aa].nex[i2]);
end;

begin
     readln(n,m);
     fillchar(e,sizeof(e),0);
     fillchar(num,sizeof(num),0);
     fillchar(cost,sizeof(cost),0);
     ans:=0;
     for i:=1 to n-1 do begin
         read(a,b);
         readln(c);
         if c>0 then begin
            inc(num[a]);
            inc(num[b]);
            e[a,num[a]]:=b;
            e[b,num[b]]:=a;
            cost[a,num[a]]:=c;
            cost[b,num[b]]:=c;
            ans:=ans+c;
         end;
     end;
     fillchar(tree,sizeof(tree),0);
     fillchar(mark,sizeof(mark),0);
     find(1);
     k:=0;
     while k<n-1-m do begin
           c:=-1;
           for i:=1 to n do if (mark[i]=0)and((c=-1)or(c>tree[i].val)) then begin
               c:=tree[i].val;
               t:=i;
           end;
           inc(k);
           mark[t]:=-1;
           ans:=ans-c;
           dec(mark[tree[t].bef]);
     end;
     writeln(ans);
end.