如何在Perl中进行整数除法OR如何使二进制搜索工作？ [英] How can I make integer division in Perl OR How can I make my binary search work?

问题描述

我正在尝试实现二进制搜索。这是我的代码：

I'm trying to implement binary search. This is my code:

#!/usr/bin/perl
#use strict;
use warnings;

@array = (1..100);
$number = <STDIN>;
$low = 0;
$high = $#array;

while($low < $high){
    print "Searcing $low ---- $high \n";
    $mid = $low + ($high - $low)/2;
    if($array[$mid] == $number){
        print "Found in index:" . $mid;
        last;
    }
    elsif($array[$mid] < $number){
        $low = $mid + 1;
    }
    else{
        $high = $mid - 1;
    }   
}

但它虽然直截了当但不起作用实现（至少它将使用Java）。

似乎我在分割时得到浮点值而无法搜索。如果我提供输入 5 我得到垃圾：

But it does not work although it is a straight forward implementation (at least it would be in Java).
It seems that I get float values when dividing and can not search. If I provide as input 5 I get garbage:

5  
Searcing 0 ---- 99  
Searcing 0 ---- 48.5  
Searcing 0 ---- 23.25  
Searcing 0 ---- 10.625  
Searcing 0 ---- 4.3125  
Searcing 3.15625 ---- 4.3125  

如何使用整数数字，所以我可以索引数组？

此外，如果我取消注释使用严格我会收到以下错误。他们的意思是什么？

How can I make it use integer numbers so I can index the array?
Also if I uncomment use strict I get the following errors. What do they mean?

Global symbol "@array" requires explicit package name at D:\Development\Perl\chapter3\binarySearch.pl line 6.  
Global symbol "$number" requires explicit package name at D:\Development\Perl\chapter3\binarySearch.pl line 9.  
Global symbol "$low" requires explicit package name at 

推荐答案

您应该使用函数 int 。

除此之外，你需要使用strict; 并使用 my 来确定变量的范围。这将捕获您可能错过的错误。只需声明它们：

Aside from that, you need to use strict; and use my to scope your variables. This will catch errors that you might miss. Just declare them like this:

my @array = (1..100);
chomp(my $number = <STDIN>);
my $low = 0;
my $high = $#array;

my $mid = int ($low + ($high - $low)/2);

您可以考虑使用 chomp 也可以从输入中删除换行符。

You might consider using chomp too, to remove newlines from your input.

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