2017.6.4 入门组 NO.2——睡眠

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其实这题就是将第二个时间-第一个时间，小于0的补全就A了

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代码如下：

var  x,y,k:string;
     l1,l2,x1,x2,x3,y1,y2,y3:longint;
begin
  readln(x);
  readln(y);
  l1:=pos(':',x);
  l2:=pos(':',y);
  k:=copy(x,1,2); val(k,x1);
  k:=copy(x,l1+1,2); val(k,y1);
  k:=copy(y,1,2); val(k,x2);
  k:=copy(y,l2+1,2); val(k,y2);
  x3:=x1-x2;
  y3:=y1-y2;
  if y3<0 then
    begin
      y3:=y3+60;
      x3:=x3-1;
    end;
  if x3<0 then
    begin
      x3:=x3+24;
    end;
  if x3<10 then
    begin
      write('0',x3,':');
      if y3<10 then write('0',y3) else write(y3);
    end
  else
    if y3<10 then
      begin
        write(x3,':0',y3);
      end
    else write(x3,':',y3);
end.