First of all, MD5 is broken - you can generate a collision, so MD5 should not be used for any security applications. SHA1 is not known to be broken and is believed to be secure. Other than that - yes, MD5 is faster but has 128-bit output, while SHA1 has 160-bit output.

**Update:** SHA1 has been broken: a team of researchers at Google and CWI have published a collision - [https://shattered.io/static/shattered.pdf][2]

  [2]: https://shattered.io/static/shattered.pdf

Here is the comparison between MD5 and SHA1. You can get a clear idea about which one is better. 


[![enter image description here][1]][1]


  [1]: http://i.stack.imgur.com/nGLE1.png

MD5 is not suitable for use for with any sort of sensitive information. Collisions exist with the algorithm, and there have been successful attacks against it. 

At the time of this update (3/2017) SHA-2 is now preferred.

When ever you embark on securely dealing with information, it is recommended that you check the latest guidelines.

I searched, but surprisingly couldn&#39;t find an answer.

I have a long `NSString` that I want to shorten. I want the maximum length to be around 20 characters. I read somewhere that the best solution is to use `substringWithRange`. Is this the best way to truncate a string? 

	NSRange stringRange = {0,20};
	NSString *myString = @&quot;This is a string, it&#39;s a very long string, it&#39;s a very long string indeed&quot;;
	NSString *shortString = [myString substringWithRange:stringRange];

It seems a little delicate (crashes if the string is shorter than the maximum length). I&#39;m also not sure if it&#39;s Unicode-safe. Is there a better way to do it? Does anyone have a nice category for this?

How can I truncate an NSString to a set length?

What do functional programmers mean when they say a certain thing is composable or not composable? 

Some of the statements of this sort that I&#39;ve read are:

- Control structures are not composable.
- Threads do not compose.
- Monadic operations are composable.

What does composability mean in context of functional programming?

&gt;**Which is the best overall hashing algorithm in terms of complexity and security? md5 or sha1?**

From what I know *md5* is faster than *sha1* but *SHA1* is more complex than md5. 

Am I missing anything?


Algorithm Complexity &amp; Security: MD5 or SHA1?

>Which is the best overall hashing algorithm in terms of complexity and security? md5 or sha1?
From what I know md5 is faster than sha1 but SHA1 is more complex than md5.
Am I missing anything?

Is there a standard function that returns the position (not value) of the maximum element of an array of values?

For example:

Suppose I have an array like this:

    sampleArray = [1, 5, 2, 9, 4, 6, 3]

I want a function that returns the integer of 3 that tells me that `sampleArray[3]` is the largest value in the array.


Finding the position of the maximum element

I&#39;m looking for a good algorithm to get all the elements in one array that are not elements in another array.  So given these arrays:

    var x = [&quot;a&quot;,&quot;b&quot;,&quot;c&quot;,&quot;t&quot;];
    var ​​​​​​​​​y = [​​​​​​​&quot;d&quot;,&quot;a&quot;,&quot;t&quot;,&quot;e&quot;,&quot;g&quot;];

I want to end up with this array:

    var z = [&quot;d&quot;,&quot;e&quot;,&quot;g&quot;];

I&#39;m using jquery, so I can take advantage of `$.each()` and `$.inArray()`. Here&#39;s the solution I&#39;ve come up with, but it seems like there should be a better way.

    // goal is to get rid of values in y if they exist in x
    var x = [&quot;a&quot;,&quot;b&quot;,&quot;c&quot;,&quot;t&quot;];
    var y = [&quot;d&quot;,&quot;a&quot;,&quot;t&quot;,&quot;e&quot;,&quot;g&quot;];
      
    var z = [];
    $.each(y, function(idx, value){
      if ($.inArray(value,x) == -1) {
        z.push(value);
      }
    });
    ​alert(z);  // should be [&quot;d&quot;,&quot;e&quot;,&quot;g&quot;]
    
Here is the [code in action][1]. Any ideas?


  [1]: http://jsbin.com/axahi3/edit

Javascript algorithm to find elements in array that are not in another array

You are going on a one-way indirect flight trip that includes &lt;strike&gt;billions&lt;/strike&gt; *an unknown very large number* of transfers. 

- You are not stopping twice in the same airport. 
- You have 1 ticket for each part of your trip. 
- Each ticket contains **src** and **dst** airport. 
- All the tickets you have are randomly sorted. 
- You forgot the original departure airport (very first src) and your destination (last dst).

Design an algorithm to reconstruct your trip with minimum big-**O** complexity.


&lt;hr&gt;

Attempting to solve this problem I have started to use a [symmetric difference][1] of two sets, Srcs and Dsts:

1)Sort all src keys in array Srcs &lt;br&gt;
2)Sort all dst keys in array Dsts &lt;br&gt;
3)Create an union set of both arrays to find non-duplicates - they are your first src and last dst &lt;br&gt;
4)Now, having the starting point, traverse both arrays using the binary search.

But I suppose there must be another more effective method.


  [1]: http://en.wikipedia.org/wiki/Symmetric_difference

One-way flight trip problem

Is there any built-in functionality in [tag:VBA] to get unique values from a one-dimensional array? What about just getting rid of duplicates?

If not, then how would I get the unique values from an array?

vba: get unique values from array

I am looking for color space converter from RGB to HSV, specifically for the range 0 to 255 for both color spaces.

Algorithm to convert RGB to HSV and HSV to RGB in range 0-255 for both

Is there a way to flatten a hash into a string, with optional delimiters between keys and values, and key/value pairs?

For example, `print {:a =&gt; :b, :c =&gt; :d}.flatten(&#39;=&#39;,&#39;&amp;&#39;)` should print `a=b&amp;c=d`

I wrote some code to do this, but I was wondering if there was a neater way:

    class Hash
      def flatten(keyvaldelimiter, entrydelimiter)
        string = &quot;&quot;
        self.each do
          |key, value|
          key = &quot;#{entrydelimiter}#{key}&quot; if string != &quot;&quot; #nasty hack
          string += &quot;#{key}#{keyvaldelimiter}#{value}&quot;  
        end
        return string
      end
    end
    
    print {:a =&gt; :b, :c =&gt; :d}.flatten(&#39;=&#39;,&#39;&amp;&#39;) #=&gt; &#39;c=d&amp;a=b&#39;

Thanks

Flattening hash into string in Ruby

I have a model that has an attribute that is an Array. What&#39;s the proper way for me to populate that attribute from a form submission?

I know having a form input with a field whose name includes brackets creates a hash from the input. Should I just be taking that and stepping through it in the controller to massage it into an array?

Example to make it less abstract:

    class Article
      serialize :links, Array
    end

The links variable takes the form of a an array of URLs, i.e. `[[&quot;http://www.google.com&quot;], [&quot;http://stackoverflow.com&quot;]]`

When I use something like the following in my form, it creates a hash:
    
    &lt;%= hidden_field_tag &quot;article[links][#{url}]&quot;, :track, :value =&gt; nil %&gt;

The resultant hash looks like this: 

    &quot;links&quot; =&gt; {&quot;http://www.google.com&quot; =&gt; &quot;&quot;, &quot;http://stackoverflow.com&quot; =&gt; &quot;&quot;}

If I don&#39;t include the url in the name of the link, additional values clobber each other:
    
    &lt;%= hidden_field_tag &quot;article[links]&quot;, :track, :value =&gt; url %&gt;

The result looks like this: `&quot;links&quot; =&gt; &quot;http://stackoverflow.com&quot;`

Ruby on Rails: Submitting an array in a form

This Ruby code is not behaving as I would expect:

    # create an array of hashes
    sort_me = []
    sort_me.push({&quot;value&quot;=&gt;1, &quot;name&quot;=&gt;&quot;a&quot;})
    sort_me.push({&quot;value&quot;=&gt;3, &quot;name&quot;=&gt;&quot;c&quot;})
    sort_me.push({&quot;value&quot;=&gt;2, &quot;name&quot;=&gt;&quot;b&quot;})
    
    # sort
    sort_me.sort_by { |k| k[&quot;value&quot;]}

    # same order as above!
    puts sort_me

I&#39;m looking to sort the array of hashes by the key &quot;value&quot;, but they are printed unsorted.


How do I sort an array of hashes by a value in the hash?

I don&#39;t have much programming experience. But, to me, Struct seems somewhat similar to Hash.

* What can Struct do well?
* Is there anything Struct can do, that Hash cannot do?

After googling, the concept of Struct is important in C, but I don&#39;t know much about C.

When to use Struct instead of Hash in Ruby?

I have two arrays

    a = [:foo, :bar, :baz, :bof]

and

    b = [&quot;hello&quot;, &quot;world&quot;, 1, 2]

I want

    {:foo =&gt; &quot;hello&quot;, :bar =&gt; &quot;world&quot;, :baz =&gt; 1, :bof =&gt; 2}

Any way to do this?

Content Type	Original Author	Original Content on Stackoverflow
Question	Starx	View Question on Stackoverflow
Solution 1 - Algorithm	sharptooth	View Answer on Stackoverflow
Solution 2 - Algorithm	Biswajit Karmakar	View Answer on Stackoverflow
Solution 3 - Algorithm	Alan	View Answer on Stackoverflow

Algorithm Complexity & Security: MD5 or SHA1?

Algorithm Problem Overview

Algorithm Solutions

Solution 1 - Algorithm

Solution 2 - Algorithm

Solution 3 - Algorithm

What does composability mean in context of functional programming?

How can I truncate an NSString to a set length?

Attributions