# Find the overlapping sum of two arrays

Given two arrays A[] and B[] having n unique elements each. The task is to find the overlapping sum of the two arrays. That is the sum of elements which is common in both of the arrays.

Note: Elements in the arrays are unique. That is the array does not contains duplicates.

Examples:

```Input : A[] = {1, 5, 3, 8}
B[] = {5, 4, 6, 7}
Output : 10
Explanation : The element which is common in both arrays is 5.
Therefore, the overlapping sum will be (5+5) = 10

Input : A[] = {1, 5, 3, 8}
B[] = {5, 1, 8, 3}
Output : 99
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Brute Force Method : The simple approach is that for each element in A[] check whether it is present in B[] and if it is present in B[] then add that number two times(once for A[] and once for B[]) to the sum. Repeat this procedure for all elements in the array A[].
Time Complexity: O(n^2).

Efficient Method : An efficient method is to use Hashing. Traverse both of the arrays and insert the elements into a hash table to keep track of the count of elements. Add the elements to sum whose count equals to two.

Below is the implementation of above approach:

## CPP

 `// CPP program to find overlapping sum ` `#include ` `using` `namespace` `std; ` ` `  `// Function for calculating ` `// overlapping sum of two array ` `int` `findSum(``int` `A[], ``int` `B[], ``int` `n) ` `{    ` `    ``// unordered map to store count of  ` `    ``// elements ` `    ``unordered_map<``int``,``int``> hash; ` `     `  `    ``// insert elements of A[] into ` `    ``// unordered_map ` `    ``for``(``int` `i=0;isecond)==2) ` `        ``{ ` `            ``sum += (itr->first)*2; ` `        ``} ` `    ``} ` `     `  `    ``return` `sum; ` `} ` ` `  `// driver code ` `int` `main() ` `{ ` `    ``int` `A[] = { 5, 4, 9, 2, 3 }; ` `    ``int` `B[] = { 2, 8, 7, 6, 3 }; ` ` `  `    ``// size of array ` `    ``int` `n = ``sizeof``(A) / ``sizeof``(A[0]); ` ` `  `    ``// function call ` `    ``cout << findSum(A, B, n); ` `     `  `    ``return` `0; ` `} `

## Python

 `# Python3 program to find overlapping sum ` ` `  `# Function for calculating ` `# overlapping sum of two array ` `def` `findSum(A, B, n): ` `     `  `    ``# unordered map to store count of ` `    ``# elements ` `    ``hash``=``dict``() ` ` `  `    ``# insert elements of A into ` `    ``# unordered_map ` `    ``for` `i ``in` `range``(n): ` `        ``hash``[A[i]] ``=` `hash``.get(A[i], ``0``) ``+` `1` ` `  `    ``# insert elements of B into ` `    ``# unordered_map ` `    ``for` `i ``in` `range``(n): ` `        ``hash``[B[i]] ``=` `hash``.get(B[i], ``0``) ``+` `1` ` `  ` `  `    ``# calculate overlapped sum ` `    ``sum` `=` `0` ` `  `    ``for` `i ``in` `hash``: ` `        ``if` `hash``[i] ``=``=` `2``: ` `            ``sum` `+``=` `i ``*` `2` ` `  `    ``return` `sum` ` `  `# Driver code ` ` `  `A ``=` `[ ``5``, ``4``, ``9``, ``2``, ``3` `] ` `B ``=` `[ ``2``, ``8``, ``7``, ``6``, ``3` `] ` ` `  `# size of array ` `n ``=` `len``(A) ` ` `  `# function call ` `print``(findSum(A, B, n)) ` ` `  `# This code is contributed by mohit kumar 29 `

Output:

```10
```

Time Complexity: O(n)
Auxiliary Space: O(n)

This article is contributed by Shivam Pradhan (anuj_charm). If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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Improved By : mohit kumar 29

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