Spfa算法模版

{<spfa><O(KM)>}const maxn=5000;type    link=^node;    node=record x,dis:longint; next:link; end;var   g:array[1..maxn] of link;   dist,q:array[1..maxn] of longint;   v:array[1..maxn] of boolean;   n:longint;procedure spfa(s:longint);var   top,i,nowi:longint;   p:link;begin     for i:=1 to n do begin dist[i]:=maxlongint; v[i]:=false; end; dist[s]:=0; v[s]:=true;     top:=1; q[1]:=s;     while top>0 do begin           nowi:=q[top]; v[nowi]:=false; dec(top);           p:=g[nowi];           while p<>nil do begin                 if dist[nowi]+p^.dis<dist[p^.x] then begin                    dist[p^.x]:=dist[nowi]+p^.dis;                    if not v[p^.x] then begin                       inc(top);                       q[top]:=p^.x;                       v[p^.x]:=true;                    end;                 end;                 p:=p^.next;           end;     end;end;