最小生成树Prim——最短网络（洛谷1546）（USACO 3.1.1）可当Prim模板

var n,m,i,j,k,s,t,p,min:longint;

    dis:array[0..100] of longint;

    f:array[0..100] of boolean;

    map:array[0..100,0..100] of longint;

procedure prim;

var i,j:longint;

begin

  fillchar(f,sizeof(f),true);

  f[1]:=false;

  for i:=1 to n do dis[i]:=map[1,i];//记录第一个点的到其它点距离

  for i:=1 to n-1 do

    begin

       //找出当前点到其它点的最小值，并记录新的点P

      min:=maxlongint;

      for j:=1 to n do

        if f[j] and (min>dis[j]) then

          begin

            min:=dis[j];

            p:=j;

          end;

      f[p]:=true;//新的最小值的点不再参与比较

      s:=s+dis[p];//记录最短值

      for j:=1 to n do  //新点到其它点的距离与原距离比较并更新小的

        if f[j] and (dis[j]>map[p,j]) then

          dis[j]:=map[p,j];

    end;

end;

begin

  readln(n);

  for i:=1 to n do

    begin

      for j:=1 to n do read(map[i,j]);

      readln;

    end;

   prim;

  writeln(s);

end.