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1. Top results related to common elements in 3 arrays

   • common elements in two lists python

     Top Answer

     Answered Dec 19, 2012 · 8 votes

     Look closely, your first list is actually a list with one item, a big string.

     >>> list1= ["'HZ1398043','HZ1395693','HZ1395532','HZ1395240','HZ1395194','HZ1395113','HZ1395036','HZ1395236','HZ1396139','HZ1398028','HZ1395098','HZ1395998','HZ1395018','HZ1395829','HZ1398031','HZ1395708','HZ1398029','HZ1398030','HZ1398054''"]>>> len(list1)1-

     Ideally, fix wherever you are getting the data to give you the right thing, if that's not possible, then you will need to parse the data.

     You will want to do something like list1 = [item.strip("'") for item in list1[0].split(",")] to get the actual list (a simple list comprehension), then use one of your methods (the set method is the most efficient, although if you wish the keep duplicates and order, you will need to do the second method, although you can improve it by making a set of list2 beforehand to check for membership in).

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     1/5

   • Common elements in two lists

     Top Answer

     Answered May 25, 2023 · 194 votes

     Use Collection#retainAll()

     .

     listA.retainAll(listB);// listA now contains only the elements which are also contained in listB.-

     If you want to avoid that changes are being affected in listA, then you need to create a new one.

     List<Integer> common = new ArrayList<>(listA);common.retainAll(listB);// common now contains only the elements which are contained in listA and listB.-

     If you're a fan of streams, best what you could do is to Stream#filter()

     on Collection#contains()

     of the other list.

     List<Integer> common = listA.stream().filter(listB::contains).toList();// common now contains only the elements which are contained in listA and listB.-

     It's only at least twice slower.

     Other Answers

     Answered Nov 09, 2019 · 45 votes

     You can use set intersection operations with your ArrayList objects.

     Something like this:

     List<Integer> l1 = new ArrayList<Integer>();-l1.add(1);l1.add(2);l1.add(3);List<Integer> l2= new ArrayList<Integer>();l2.add(4);l2.add(2);l2.add(3);System.out.println("l1 == "+l1);System.out.println("l2 == "+l2);List<Integer> l3 = new ArrayList<Integer>(l2);l3.retainAll(l1); System.out.println("l3 == "+l3);

     Now, l3 should have only common elements between l1 and l2.

     CONSOLE OUTPUTl1 == [1, 2, 3]l2 == [4, 2, 3]l3 == [2, 3]

     Other Answers

     Answered Jan 09, 2019 · 44 votes

     Why reinvent the wheel? Use Commons Collections:

     CollectionUtils.intersection(java.util.Collection a, java.util.Collection b)-

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     2/5

   • Common elements in a dataframe column

     Top Answer

     Answered Jun 11, 2018 · 0 votes

     You can do something like:

     df1 = pd.DataFrame([ (0, "A"), (1, "B"), (2, "C"), (3, "D")], columns=["id", "val"])df2 = pd.DataFrame([ (0, "A"), (1, "A"), (2, "A"), (3, "D")], columns=["id", "val"])df3 = pd.DataFrame([ (0, "A"), (1, "A"), (2, "A"), (3, "A")], columns=["id", "val"])from functools import reducedfs = [df1, df2, df3]val = reduce( lambda acc, x: np.intersect1d(acc, x['val']), dfs, dfs[0]['val'])val# array(['A'], dtype=object)

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     3/5

   • Common elements between two lists and preserving the order of elements in the two lists

     Top Answer

     Answered Jan 10, 2014 · 4 votes

     list1 = ['a', 'e', 't', 'b', 'c']list2 = ['e', 'b', 'a', 'c', 'n', 's']-weights = defaultdict(int)-for i, e in enumerate(list1): weights[e] += ifor i, e in enumerate(list2): weights[e] += i>>> result = sorted(set(list1) & set(list2), key=lambda i: weights[i])>>> result['e', 'a', 'b', 'c']

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     4/5

   • Common elements in all rows of a given matrix

     Given an m x n matrix, find all common elements present in all rows in O(mn) time and one traversal of matrix.

     Example:

     Output:

     Input:mat[4][5] = {{1, 2, 1, 4, 8}, {3, 7, 8, 5, 1}, {8, 7, 7, 3, 1}, {8, 1, 2, 7, 9}, };Output: 1 8 or 8 18 and 1 are present in all rows.

     A simple solution is to consider every element and check if it is present in all rows. If present, then print it.  A better solution is to sort all rows in the matrix and use similar approach as discussed here. Sorting will take O(mnlogn) time and finding common elements will take O(mn) time. So overall time complexity of this solution is O(mnlogn)

     Can we do better than O(mnlogn)?  The idea is to use maps. We initially insert all elements of the first row in an map. For every other element in remaining rows, we check if it is present in the map. If it is present in the map and is not duplicated in current row, we increment count of the element in map by...

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     5/5

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2. www.geeksforgeeks.org › find-common-elements-threeFind common elements in three sorted arrays - GeeksforGeeks

   www.geeksforgeeks.org › find-common-elements-three

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   May 28, 2024 · Steps: Follow the given steps to solve the problem: Initialize an empty reference list (ref) and a final list (final) to store common elements. Iterate through each element in the first array (ar1). Check if the current element exists in the second array (ar2). If found, append it to the reference list (ref).

3. www.geeksforgeeks.org › array-data-structure-guideArray Data Structure Guide - GeeksforGeeks

   www.geeksforgeeks.org › array-data-structure-guide

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   May 22, 2024 · Common operations performed on arrays include: Traversal : Visiting each element of an array in a specific order (e.g., sequential, reverse). Insertion : Adding a new element to an array at a specific index. Deletion : Removing an element from an array at a specific index. Searching : Finding the index of an element in an array. Applications of ...

4. www.geeksforgeeks.org › javascript-program-to-findJavaScript Program to Find Common Elements ... - GeeksforGeeks

   www.geeksforgeeks.org › javascript-program-to-find

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   Jun 4, 2024 · Given two sorted arrays, our task is to find common elements in two sorted arrays then the program should return an array that contains all the elements that are common to the two arrays. The arrays can contain duplicate elements, that is, values at one index in an array can be equal to the values at another index in the array. Example:

5. coderspacket.com › posts › how-to-find-commonHow to Find common elements from an array in C++

   coderspacket.com › posts › how-to-find-common

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   Jun 6, 2024 · Here we use operations like bitsets to represent the presence of elements and then perform bitwise AND operation to find common elements. This approach is efficient but requires a limited range of numbers. Some standard libraries provide set intersection algorithms like std::set_intersection, which can efficiently find common elements between ...

6. www.simplilearn.com › arrays-in-data-structureArrays in Data Structure: A Guide With Examples - Simplilearn

   www.simplilearn.com › arrays-in-data-structure

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   Jun 5, 2024 · An array is a linear data structure that collects elements of the same data type and stores them in contiguous and adjacent memory locations. Arrays work on an index system starting from 0 to (n-1), where n is the size of the array. It is an array, but there is a reason that arrays came into the picture.

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7. www.learncpp.com › introduction-to-stdarray17.1 — Introduction to std::array – Learn C++ - LearnCpp.com

   www.learncpp.com › introduction-to-stdarray

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   May 28, 2024 · A std::array can be const:. #include <array> int main() { const std::array<int, 5> prime { 2, 3, 5, 7, 11 }; return 0; } Even though the elements of a const std::array are not explicitly marked as const, they are still treated as const (because the whole array is const).

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   • There are two main types of arrays: One-dimensional arrays: These arrays store a single row of elements. Multidimensional arrays: These arrays store multiple rows of elements. Common operations performed on arrays include: Traversal : Visiting each element of an array in a specific order (e.g., sequential, reverse).

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   What is a one dimensional array?

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   What is an array used for?

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9. www.scholarhat.com › one-dimensional-arrayOne dimensional Array in Data Structures with Example

   www.scholarhat.com › one-dimensional-array

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   Jun 6, 2024 · Then calculate and print the sum of all elements in the array. Output Elements of the array: 10 20 30 40 50 Updated array after changing the third element: 10 20 35 40 50 Sum of the elements: 155 Applications in DSA 1. Linear Search. One-dimensional arrays are commonly used in linear search algorithms to find the position of a specific element ...