[英]Problem with binary search algorithm in ruby
def binarysearch(a, b, tofind, stringarray)
k=(a+b)/2
if a==b
return nil
end
if (stringarray[k]).include? tofind
return stringarray[k]
end
if (stringarray[k]<=>tofind)==1
binarysearch(a,k,tofind,stringarray)
end
if (stringarray[k]<=>tofind)==-1
binarysearch(k,b,tofind,stringarray)
end
if (stringarray[k]<=>tofind)==0
return stringarray[k]
end
end
This is a binary search algorithm. 这是一个二进制搜索算法。 The a and b are the array indices that it is working on, tofind is a string that it is searching for, and stringarray is an array of strings.
a和b是它正在处理的数组索引,tofind是它正在搜索的字符串,stringarray是一个字符串数组。 Unfortunately, every time that I try to run this function I get the following syntax error:
不幸的是,每次我尝试运行此函数时,都会出现以下语法错误:
undefined method `include?' for 1:Fixnum (NoMethodError)`
But this is not a fixnum. 但这不是一个fixnum。 I am pretty new to Ruby, so I could easily be missing something obvious.
我是Ruby的新手,所以我很容易错过明显的东西。 Any advice?
有什么建议吗?
This is where I declare stringarray: (Netbeans says that it is an array) 这是我声明stringarray的地方:(Netbeans说这是一个数组)
strings=Array.new
newstring=""
until newstring=="no" do
newstring=gets.chomp
strings[strings.size]=newstring
end
This adds binary search to all arrays: 这将二进制搜索添加到所有数组:
class Array
def binarysearch(tf,lower=0,upper=length-1)
return if lower > upper
mid = (lower+upper)/2
tf < self[mid] ? upper = mid-1 : lower = mid+1
tf == self[mid] ? mid : binarysearch(tf,lower,upper)
end
end
Then you can use it like this: 然后,您可以像这样使用它:
(0..100).to_a.binarysearch(25)
=> 25
(0..100).to_a.binarysearch(-1)
=> nil
Or specify your lower and upper bound from the beginning: 或者从一开始就指定您的上限和下限:
(0..100).to_a.binarysearch(25, 50, 100)
=> nil
The stringarray
that is passed to your function is not actually an array of strings, but just a simple string. 传递给您的函数的
stringarray
实际上不是字符串数组,而仅仅是一个简单的字符串。 Using the []
method on a string returns the character code of the character at the given position, as a Fixnum; 在字符串上使用
[]
方法会返回给定位置的字符的字符代码,即Fixnum。 so stringarray[k] returns the character code of the character at position k in the string. 因此stringarray [k]返回字符串中位置k处的字符的字符代码。 And as the error says, Fixnum does not have an
include?
并且如错误所述,Fixnum没有
include?
. 。
Even if stringarray was an array of strings, I'm not sure why you would do string comparisons with include?
即使stringarray 是字符串数组,我也不知道为什么要使用
include?
进行字符串比较include?
. 。
include?
is for finding out if items exist in an array. 用于确定数组中是否存在项。 To compare strings, just use
==
. 要比较字符串,只需使用
==
。
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