KM 最大权匹配

http://unbelievable.ycool.com/post.1176914.html

 

如果是求 最小权， 把map中的值变成负数

x, y : array [1..maxn] of boolean;
lx, ly : array [1..maxn] of longint;
map : array [1..maxn,1..maxn] of longint;

procedure prepare;
var i, j : longint;
begin
  for i:=1 to n do
    for j:=1 to n do
      if map[i,j]>lx[i] then lx[i]:=map[i,j];
end;

function search(k : longint) : boolean;
var i : longint;
begin
  search:=true; x[k]:=true;
  for i:=1 to n do
    if not y[i] and (lx[k]+ly[i]=map[k,i]) then begin
      y[i]:=true; tmp:=match[i]; match[i]:=k;
      if (tmp=0) or search(tmp) then exit;
      match[i]:=tmp;
    end;
  search:=false; 
end;

procedure km;
var i, j, k : longint;
begin
  for k:=1 to n do
    repeat
      fillchar(x,sizeof(x),0);
      fillchar(y,sizeof(y),0);
      if search(k) then break;
      d:=maxlongint;
      for i:=1 to n do
        if x[i] then
          for j:=1 to n do
            if not y[j] then
              if lx[i]+ly[j]-map[i,j]<d then d:=lx[i]+ly[j]-map[i,j];
      for i:=1 to n do begin
        if x[i] then dec(lx[i],d);
        if y[i] then inc(ly[i],d);
      end;
    until false;
end;

procedure getans;
var ans, i : longint;
begin
  ans:=0;
  for i:=1 to n do
    inc(ans,map[match[i],i]);
end;