Basic Pascal Tutorial/Chapter 3/Solution/zh CN

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3Ea - 参考答案 (原作者: Tao Yue, 状态: 未更改)

斐波那契数列参考答案

(* Author:    Tao Yue
   Date:      19 July 1997
   Description:
      Find the first 10 Fibonacci numbers
   Version:
      1.0 - original version
*)

program Fibonacci;

var
   Fibonacci1, Fibonacci2 : integer;
   temp : integer;
   count : integer;

begin    (* Main *)
   writeln ('First ten Fibonacci numbers are:');
   count := 0;
   Fibonacci1 := 0;
   Fibonacci2 := 1;
   repeat
      write (Fibonacci2:7);
      temp := Fibonacci2;
      Fibonacci2 := Fibonacci1 + Fibonacci2;
      Fibonacci1 := Temp;
      count := count + 1
   until count = 10;
   writeln;

   (* Of course, you could use a FOR loop or a WHILE loop
      to solve this problem. *)

end.     (* Main *)

平方问题参考答案

(* Author:    Tao Yue
   Date:      13 July 2000
   Description:
      Display all powers of two up to 20000, five per line
   Version:
      1.0 - original version
*)

program PowersofTwo;

const
   numperline = 5;
   maxnum = 20000;
   base = 2;

var
   number : longint;
   linecount : integer;

begin    (* Main *)
   writeln ('Powers of ', base, ', 1 <= x <= ', maxnum, ':');
   (* Set up for loop *)
   number := 1;
   linecount := 0;
   (* Loop *)
   while number <= maxnum do
      begin
         linecount := linecount + 1;
         (* Print a comma and space unless this is the first
            number on the line *)
         if linecount > 1 then
            write (', ');
         (* Display the number *)
         write (number);
         (* Print a comma and go to the next line if this is
            the last number on the line UNLESS it is the
            last number of the series *)
         if (linecount = numperline) and not (number * 2 > maxnum) then
            begin
               writeln (',');
               linecount := 0
            end;
         (* Increment number *)
         number := number * base;
      end;  (* while *)
   writeln;

   (* This program can also be written using a
      REPEAT..UNTIL loop. *)

end.     (* Main *)

注意，我使用三个常量：numperline为控制显示数目，maxnum为最大值，base为指数；以确保程序可以适应以后。

使用常量，而不是文本是一个良好的编程习惯。当程序很长，上千行代码，找起来会很麻烦，你不能简单使用全文搜索和替换。使用常量使得它更简单也易于扩展。

另外注意，number变量为长整型而不是整型，这是因为测试时 number <= 20000 时失败了。整型的范围在 -32768..32767（尝试使用整型，看看会发生什么）。

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