usaco 2.4 comehome 2008.7.16

usaco 2.4 comehome 2008.7.16

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1.路是双向的，不是单项的。

2.起始时读入数据出错，当读入一条路x[l1,l2]时，要从x[l2,l1]和x[l1,l2]中选择一条小的（当然，都要大于零），否则就不能得到最优的解。这点题目中似乎暗示了，我却没注意到}

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ID:

PROG:comehome

LANG:PASCAL

}

program p_comehome;const fin='comehome.in';fout='comehome.out';    nn=52;var a:array['A'..'Z']of longint;    b:array['a'..'z']of longint;    x:array[1..nn,1..nn]of longint;    ch:string;f1,f2:text;u,op,w:char;    la,k,max,code,s,n,pz,i,j,l,l1,l2,maxnn:longint;function deal(t:char):longint;begin   if t<'a' then      begin        if (t>op) and (t<>'Z') then op:=t;        if a[t]=0 then                begin                  inc(l);a[t]:=l;                   inc(la);                  exit(l)                end else exit(a[t])      end      else       begin         if b[t]=0 then               begin                 inc(l);b[t]:=l;                 exit(l)               end else exit(b[t])       end;end;procedure init;begin   op:='A';la:=0;   fillchar(a,sizeof(a),0);   fillchar(b,sizeof(b),0);   for i:=1 to nn do for j:=1 to nn do      x[i,j]:=99999999;   assign(f1,fin);reset(f1);   assign(f2,fout);rewrite(f2);   readln(f1,n);l:=0;   for i:=1 to n do     begin       readln(f1,ch);       val(copy(ch,5,length(ch)-4),s,code);       l1:=deal(ch[1]);l2:=deal(ch[3]);       x[l1,l2]:=s;       if x[l2,l1]<x[l1,l2] then x[l1,l2]:=x[l2,l1] else         x[l2,l1]:=x[l1,l2];     end;end;procedure choose;begin  for k:=1 to l do    for i:=1 to l do     if i<>k then      for j:=1 to l do       if (j<>k)and(i<>j)then        if (x[i,j]>x[i,k]+x[k,j])then            x[i,j]:=x[i,k]+x[k,j];        end;{-----------------------main---------------------------}begin  max:=maxlongint;  init;  choose;  for w:='A' to 'Y' do   if a[w]<>0 then   begin    if x[a[w],a['Z']]<max then        begin max:=x[a[w],a['Z']];u:=w;end;   end;  writeln(f2,u,' ',max);  close(f1);  close(f2);  end.