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Sum of all minimum frequency elements in Matrix

  • Last Updated : 28 May, 2021

Given a NxM matrix of integers containing duplicate elements. The task is to find the sum of all minimum 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 : 9
The min occurring elements are 4, 5 and they 
occurs only 1 time.
Therefore, sum = 4+5 = 9

Input : mat[] = {{10, 20},
                 {40, 40}}
Output : 30

 

Approach:
 

  • Traverse the matrix and use a map in C++ 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 minimum frequency.
  • Finally, traverse the map to find the frequency of elements and check if it matches with the minimum frequency obtained in previous step, if yes, then add this element its frequency times to sum.

Below is the implementation of the above approach: 
 

C++




// C++ program to find sum of all min
// frequency elements in a Matrix
 
#include <bits/stdc++.h>
using namespace std;
 
#define N 3 // Rows
#define M 3 // Columns
 
// Function to find sum of all min
// frequency elements in a Matrix
int sumMinOccurring(int arr[N][M])
{
    // Store frequencies of elements
    // in matrix
    map<int, int> mp;
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < M; j++) {
            mp[arr[i][j]]++;
        }
    }
 
    // Find minimum frequency
    int sum = 0;
    int minFreq = INT_MAX;
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        if (itr->second < minFreq)
            minFreq = itr->second;
    }
 
    // Sum of minimum frequency elements
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        if (itr->second == minFreq) {
            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 << sumMinOccurring(mat) << endl;
 
    return 0;
}

Java




// Java program to find sum of all min
// frequency elements in a Matrix
import java.util.HashMap;
import java.util.Iterator;
 
class GFG
{
    static int N = 3; // Rows
    static int M = 3; // Columns
 
    // Function to find sum of all min
    // frequency elements in a Matrix
    public static int sumMinOccuring(int[][] arr)
    {
 
        // Store frequencies of elements
        // in matrix
        HashMap<Integer, Integer> mp = new HashMap<>();
        for (int i = 0; i < N; i++)
        {
            for (int j = 0; j < M; j++)
            {
                if (mp.containsKey(arr[i][j]))
                {
                    int x = mp.get(arr[i][j]);
                    mp.put(arr[i][j], x + 1);
                }
                else
                    mp.put(arr[i][j], 1);
            }
        }
 
        // Find minimum frequency
        int sum = 0;
        int minFreq = Integer.MAX_VALUE;
        for (HashMap.Entry<Integer,
                           Integer> entry : mp.entrySet())
        {
            if (entry.getValue() < minFreq)
                minFreq = entry.getValue();
        }
 
        // Sum of minimum frequency elements
        for (HashMap.Entry<Integer,
                           Integer> entry : mp.entrySet())
        {
            if (entry.getValue() == minFreq)
                sum += entry.getKey() * entry.getValue();
        }
 
        return sum;
    }
 
    // Driver code
    public static void main(String[] args)
    {
        int[][] mat = { { 1, 2, 3 },
                        { 1, 3, 2 },
                        { 1, 5, 6 } };
 
        System.out.println(sumMinOccuring(mat));
    }
}
 
// This code is contributed by
// sanjeev2552

Python3




# Python3 program to find sum of all min
# frequency elements in a Matrix
 
import sys
import math
 
# Store frequencies of elements
# in matrix
def sumMinOccuring(mat):
    n,m=len(mat),len(mat[0])
    _map={}
    for i in range(n):
        for j in range(m):
            d=mat[i][j]
            if d in _map:
                _map[d]=_map.get(d)+1
            else:
                _map[d]=1
 
    # Find minimum frequency
    _sum,minFreq=0,sys.maxsize
    for i in _map:
        minFreq=min(minFreq,_map.get(i))
     
    # Sum of minimum frequency elements
    for i in range(n):
        for j in range(m):
            if _map.get(mat[i][j])==minFreq:
                _sum+=mat[i][j]
     
    return _sum
  
# Driver Code
if __name__=='__main__':
    mat=[[1,2,3],[1,3,2],[1,5,6]]
    print(sumMinOccuring(mat))
 
 
# This code is Contributed by Vikash Kumar 37

C#




// C# program to find sum of all min
// frequency elements in a Matrix
using System;
using System.Collections.Generic;
 
class GFG
{
    static int N = 3; // Rows
    static int M = 3; // Columns
 
    // Function to find sum of all min
    // frequency elements in a Matrix
    public static int sumMinOccuring(int[,] arr)
    {
 
        // Store frequencies 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]))
                {
                    int x = mp[arr[i, j]];
                    mp[arr[i, j]] = x + 1;
                }
                else
                    mp[arr[i, j]] = 1;
            }
        }
 
        // Find minimum frequency
        int sum = 0;
        int minFreq = 10000009;
        foreach(KeyValuePair<int, int> ele1 in mp)
        {
            if(ele1.Value < minFreq)
                minFreq = ele1.Value;
        }
 
        // Sum of minimum frequency elements
        foreach(KeyValuePair<int, int> ele1 in mp)
        {
            if (ele1.Value == minFreq)
                sum += ele1.Key * ele1.Value;
        }
        return sum;
    }
 
    // Driver code
    public static void Main()
    {
        int[,] mat = new int[3, 3] {{ 1, 2, 3 },
                                    { 1, 3, 2 },
                                    { 1, 5, 6 }};
 
        Console.Write(sumMinOccuring(mat));
    }
}
 
// This code is contributed by
// Mohit kumar

Javascript




<script>
 
// JavaScript program to find sum of all min
// frequency elements in a Matrix
 
let N = 3; // Rows
let M = 3; // Columns
 
// Function to find sum of all min
    // frequency elements in a Matrix
function sumMinOccuring(arr)
{
    // Store frequencies of elements
        // in matrix
        let mp = new Map();
        for (let i = 0; i < N; i++)
        {
            for (let j = 0; j < M; j++)
            {
                if (mp.has(arr[i][j]))
                {
                    let x = mp.get(arr[i][j]);
                    mp.set(arr[i][j], x + 1);
                }
                else
                    mp.set(arr[i][j], 1);
            }
        }
   
        // Find minimum frequency
        let sum = 0;
        let minFreq = Number.MAX_VALUE;
        for (let [key, value] of mp.entries())
        {
            if (value < minFreq)
                minFreq = value;
        }
   
        // Sum of minimum frequency elements
        for (let [key, value] of mp.entries())
        {
            if (value == minFreq)
                sum += key * value;
        }
   
        return sum;
}
 
// Driver code
let mat=[[1,2,3],[1,3,2],[1,5,6]];
 
document.write(sumMinOccuring(mat));
 
 
// This code is contributed by patel2127
 
</script>
Output: 



11

 

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

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