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# Sum of all even frequency elements in Matrix

• Difficulty Level : Easy
• Last Updated : 08 Jul, 2021

Given a NxM matrix of integers containing duplicate elements. The task is to find the sum of all even occurring elements in the given matrix. That is the sum of all such elements whose frequency is even in the matrix.
Examples

```Input : mat[] = {{1, 1, 2},
{2, 3, 3},
{4, 5, 3}}
Output : 18
The even occurring elements are 1, 2 and their number
of occurrences are 2, 2 respectively. Therefore,
sum = 1+1+2+2 = 6.

Input : mat[] = {{10, 20},
{40, 40}}
Output : 80```

Approach:

• Traverse the matrix and use a map to store the frequency of elements of the matrix such that the key of map is the matrix element and value is its frequency in the matrix.
• Then, traverse the map to find the frequency of elements and check if it is even, then add this element it’s frequency times to sum.

Below is the implementation of the above approach:

## C++

 `// C++ program to find sum of all even``// frequency elements in a Matrix` `#include ``using` `namespace` `std;` `#define N 3 // Rows``#define M 3 // Columns` `// Function to find sum of all even``// frequency elements in a Matrix``int` `sumOddOccurring(``int` `arr[N][M])``{` `    ``// Store frequency of elements``    ``// in matrix``    ``unordered_map<``int``, ``int``> mp;``    ``for` `(``int` `i = 0; i < N; i++) {``        ``for` `(``int` `j = 0; j < M; j++) {``            ``mp[arr[i][j]]++;``        ``}``    ``}` `    ``// Sum even frequency elements``    ``int` `sum = 0;``    ``for` `(``auto` `itr = mp.begin(); itr != mp.end(); itr++) {``        ``if` `(itr->second % 2 == 0) {``            ``int` `x = itr->second;``            ``sum += (itr->first) * (itr->second);``        ``}``    ``}` `    ``return` `sum;``}` `// Driver Code``int` `main()``{` `    ``int` `mat[N][M] = { { 1, 2, 3 },``                      ``{ 1, 3, 2 },``                      ``{ 1, 5, 6 } };` `    ``cout << sumOddOccurring(mat) << endl;` `    ``return` `0;``}`

## Java

 `// Java program to find sum of all even``// frequency elements in a Matrix``import` `java.util.*;` `class` `GFG``{` `static` `final` `int` `N = ``3``; ``// Rows``static` `final` `int` `M = ``3``; ``// Columns` `// Function to find sum of all even``// frequency elements in a Matrix``static` `int` `sumOddOccurring(``int` `arr[][])``{` `    ``// Store frequency of elements``    ``// in matrix``    ``Map mp = ``new` `HashMap();``    ``for` `(``int` `i = ``0``; i < N; i++)``    ``{``        ``for` `(``int` `j = ``0``; j < M; j++)``        ``{``            ``if``(mp.get(arr[i][j]) == ``null``)``                ``mp.put(arr[i][j], ``1``);``            ``else``                ``mp.put(arr[i][j],``                      ``(mp.get(arr[i][j]) + ``1``));``        ``}``    ``}` `    ``// Sum even frequency elements``    ``int` `sum = ``0``;``    ``Set< Map.Entry > st = mp.entrySet();` `    ``for` `(Map.Entry< Integer, Integer> me:st)``    ``{``        ``if` `(me.getValue() % ``2` `== ``0``)``        ``{``            ``int` `x = me.getValue();``            ``sum += (me.getKey()) * (me.getValue());``        ``}``    ``}``    ``return` `sum;``}` `// Driver Code``public` `static` `void` `main(String args[])``{``    ``int` `mat[][] = {{ ``1``, ``2``, ``3` `},``                   ``{ ``1``, ``3``, ``2` `},``                   ``{ ``1``, ``5``, ``6` `}};` `    ``System.out.print(sumOddOccurring(mat));``}``}` `// This code is contributed by Arnab Kundu`

## Python3

 `# Python3 program to find sum of all even``# frequency elements in a Matrix``import` `sys` `N ``=` `3` `# Rows``M ``=` `3` `# Columns` `# Function to find sum of all even``# frequency elements in a Matrix``def` `sumOddOccuring(arr):` `    ``# Store frequencies of elements``    ``# in matrix``    ``mp ``=` `dict``()``    ``for` `i ``in` `range``(N):``        ``for` `j ``in` `range``(M):``            ``if` `arr[i][j] ``in` `mp:``                ``mp[arr[i][j]] ``+``=` `1``            ``else``:``                ``mp[arr[i][j]] ``=` `1` `    ``# Sum of even frequency elements``    ``s ``=` `0``    ``for` `i ``in` `mp:``        ``if` `mp[i] ``%` `2` `=``=` `0``:``            ``x ``=` `mp[i]``            ``s ``+``=` `i ``*` `mp[i]` `    ``return` `s` `# Driver code``if` `__name__ ``=``=` `"__main__"``:``    ``mat ``=` `[[``1``, ``2``, ``3``],``           ``[``1``, ``3``, ``2``],``           ``[``1``, ``5``, ``6``]]` `    ``print``(sumOddOccuring(mat))` `# This code is contributed by``# sanjeev2552`

## C#

 `// C# program to find sum of all even``// frequency elements in a Matrix``using` `System;``using` `System.Collections.Generic;` `class` `Sol``{` `static` `readonly` `int` `N = 3; ``// Rows``static` `readonly` `int` `M = 3; ``// Columns` `// Function to find sum of all even``// frequency elements in a Matrix``static` `int` `sumOddOccurring(``int` `[,]arr)``{` `    ``// Store frequency of elements``    ``// in matrix``    ``Dictionary<``int``, ``int``> mp = ``new` `Dictionary<``int``,``int``>();``    ``for` `(``int` `i = 0; i < N; i++)``    ``{``        ``for` `(``int` `j = 0; j < M; j++)``        ``{``            ``if``(!mp.ContainsKey(arr[i, j]))``                ``mp.Add(arr[i, j], 1);``            ``else``{``                ``var` `val = mp[arr[i, j]];``                ``mp.Remove(arr[i, j]);``                ``mp.Add(arr[i, j], val + 1);``            ``}``        ``}``    ``}` `    ``// Sum even frequency elements``    ``int` `sum = 0;``    ``foreach``(KeyValuePair<``int``, ``int``> entry ``in` `mp)``    ``{``        ``if``(entry.Value % 2 == 0){``            ``sum += entry.Key * entry.Value;``        ``}``    ``}` `    ``return` `sum;``}` `// Driver Code``public` `static` `void` `Main(String []args)``{` `    ``int` `[,]mat = { { 1, 2, 3 },``                    ``{ 1, 3, 2 },``                    ``{ 1, 5, 6 } };` `    ``Console.Write( sumOddOccurring(mat) );` `}``}` `/* This code contributed by PrinciRaj1992 */`

## Javascript

 ``
Output:

`10`

Time Complexity : O(N x M)
Auxiliary Space : O(N x M)

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