bzoj2539

这道题真的不难，但是细节挺多（具体见程序）
题目本身而言，显然是个费用流模型（或者写KM）

 type node=record
        point,next,flow,cost:longint;
      end;

 var p,x,y,pre,cur,d:array[..] of longint;
     v:array[..] of boolean;
     q:array[..] of longint;
     edge:array[..] of node;
     a:array[..,..] of longint;
     na:array[..] of string[];
     t,n,i,len,j,k:longint;
     ef:boolean;
     s:string;
     ch:char;

 function find(x:string):longint;
   var i:longint;
   begin
     for i:= to *n do
       if na[i]=x then exit(i);
   end;

 function check(l,r:longint):boolean;
   var i:longint;
   begin
     for i:= to *n do
       if (i<>l) and (i<>r) then
         if ((x[i]<=x[l]) and (x[i]>=x[r])) or ((x[i]>=x[l]) and (x[i]<=x[r])) then
           if ((y[i]<=y[l]) and (y[i]>=y[r])) or ((y[i]>=y[l]) and (y[i]<=y[r])) then
             if (x[i]-x[l])*(y[i]-y[r])=(x[i]-x[r])*(y[i]-y[l]) then
             begin  //注意是线段上的点
               exit(false);
             end;
     exit(true);
   end;

 procedure add(x,y,f,w:longint);
   begin
     inc(len);
     edge[len].point:=y;
     edge[len].flow:=f;
     edge[len].cost:=w;
     edge[len].next:=p[x];
     p[x]:=len;
   end;

 function spfa:boolean;
   var i,j,f,r,x,y:longint;
   begin
     for i:= to t do
       d[i]:=-;
     d[]:=;
     f:=;
     r:=;
     fillchar(v,sizeof(v),false);
     q[]:=;
     v[]:=true;
     while f<=r do
     begin
       x:=q[f];
       v[x]:=false;
       i:=p[x];
       while i<>- do
       begin
         y:=edge[i].point;
         if edge[i].flow> then
           if d[x]+edge[i].cost>d[y] then
           begin
             pre[y]:=x;
             cur[y]:=i;
             d[y]:=d[x]+edge[i].cost;
             if not v[y] then
             begin
               inc(r);
               q[r]:=y;
               v[y]:=true;
             end;
           end;
         i:=edge[i].next;
       end;
       inc(f);
     end;
     if d[t]=- then exit(false) else exit(true);
   end;

 function maxcost:longint;
   var i,j:longint;
   begin
     maxcost:=;
     while spfa do
     begin
       maxcost:=maxcost+d[t];
       i:=t;
       while i<> do
       begin
         j:=cur[i];
         dec(edge[j].flow);
         inc(edge[j xor ].flow);
         i:=pre[i];
       end;
     end;
   end;

 begin
   len:=-;
   fillchar(p,sizeof(p),);
   readln(k);
   readln(n);
   for i:= to *n do
   begin
     readln(x[i],y[i],ch,na[i]);
     for j:= to length(na[i]) do
       na[i][j]:=upcase(na[i][j]);  //注意不区分大小写
   end;
   t:=*n+;
   for i:= to n do
   begin
     add(,i,,);
     add(i,,,);
     add(i+n,t,,);
     add(t,i+n,,);
   end;

   for i:= to n do
     for j:=n+ to *n do
       a[i,j]:=;   //注意
   ef:=true;
   while ef do
   begin
     s:='';
     read(ch);
     while ch<>' ' do
     begin
       s:=s+upcase(ch);
       if s='END' then ef:=false;  //大坑，有的人名字里会带end
       read(ch);
       if not ef and (ord(ch)>=)  then
         ef:=true
       else if not ef then break;
     end;
     if not ef then break;
     i:=find(s);
     s:='';
     read(ch);
     while ch<>' ' do
     begin
       s:=s+upcase(ch);
       read(ch);
     end;
     j:=find(s);
     readln(a[i,j]);
     a[j,i]:=a[i,j];
   end;
   for i:= to n do
     for j:=n+ to *n do
       if (sqr(x[i]-x[j])+sqr(y[i]-y[j])<=sqr(k)) and check(i,j) then
       begin
         add(i,j,,a[i,j]);
         add(j,i,,-a[i,j]);
       end;
   writeln(maxcost);
 end.