Find most common value in an array

In summary, the conversation discusses finding the mode or the most common element in a list of numbers or names. The proposed solution involves sorting the list and using a function called most_common_element to find the element that occurs the most times in a row. There is a suggestion to initialize the variable mostcommon as an empty list and further updates are made to the code to improve its efficiency.
  • #1
trollcast
Gold Member
282
13

Homework Statement


Find the mode from a list of numbers or find the most common string in a list of names.

Homework Equations



The Attempt at a Solution



Code:
def most_common_element(lst):
    lst.sort()
    mostcommon = []
    mostcommonfreq = 0
    prev = 0
    count = 0

    for e in lst:
        if e != prev:
            count = 1
        if e == prev:
            count += 1

        if count == mostcommonfreq:
            mostcommon.append(e)

        if count > mostcommonfreq:
            mostcommon = [e]
            mostcommonfreq = count
        prev = e

    return mostcommon

Is there any way to make that more efficient?
 
Last edited:
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  • #2
I'm not that familiar with python (assuming this is python), but it appears that this program finds the element that occurs the most times in a row, as opposed to the most times in the list.
 
  • #3
rcgldr said:
I'm not that familiar with python (assuming this is python), but it appears that this program finds the element that occurs the most times in a row, as opposed to the most times in the list.

Sorry I should have copied more of the code.

I've sorted the list before I pass it to the most_common_element function.
 
  • #4
Since the list is sorted your code looks ok. I noticed that you initialized mostcommon = 0 as opposed to mostcommon = [] (to create an empty list). It might make the code easier to follow using mostcommon = [], since the reader will know that mostcommon is to be used as a list.
 
  • #5
rcgldr said:
Since the list is sorted your code looks ok. I noticed that you initialized mostcommon = 0 as opposed to mostcommon = [] (to create an empty list). Is this OK to do in Python?

Nope, I copied the source code from my program and then had to change it a bit so it made sense outside of the program.

I fixed it now
 
  • #6
trollcast said:
I fixed it now
After your updates, the code looks OK now.
 
Last edited:

What is the most efficient way to find the most common value in an array?

The most efficient way to find the most common value in an array is to use a hash table or dictionary data structure. This allows for constant time lookup and insertion of values, making it a faster solution compared to looping through the array and counting occurrences.

Can I use a built-in function to find the most common value in an array?

Yes, many programming languages have built-in functions for finding the most common value in an array. For example, in Python, you can use the collections.Counter() method, while in JavaScript, you can use the Array.prototype.reduce() method.

What is the time complexity of finding the most common value in an array?

The time complexity of finding the most common value in an array depends on the approach used. Using a hash table or dictionary data structure has a time complexity of O(n), while a brute force approach using nested loops has a time complexity of O(n^2).

What if there are multiple values with the same highest frequency?

If there are multiple values with the same highest frequency, you can either return all of those values or choose one randomly. Alternatively, you can also modify your approach to return the values in a sorted order.

Can I find the most common value in a multi-dimensional array?

Yes, you can find the most common value in a multi-dimensional array by first flattening the array into a one-dimensional array and then applying the same approach as you would for a regular array.

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