Find unique elements in a matrix

Given a matrix mat[][] having n rows and m columns. We need to find unique elements in matrix i.e, those elements which are not repeated in the matrix or those elements whose frequency is 1.

Examples:

Input :  20  15  30  2
         2   3   5   30
         6   7   6   8
Output : 3  20  5  7  8  15 

Input :  1  2  3  
         5  6  2
         1  3  5
         6  2  2
Output : No unique element in the matrix

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

Follow these steps to find unique element:
1. Create an empty hash table or dictionary.
2. Traverse through all the elements of the matrix
3. If element is present in the dictionary, then increment its count
4. Otherwise insert element with value = 1.

C++

// C++ program to find unique 
// element in matrix 
#include<bits/stdc++.h> 
using namespace std; 
#define R 4 
#define C 4 
  
// function that calculate unique element 
int unique(int mat[R][C], int n, int m) 
{ 
    int maximum = 0, flag = 0; 
    for(int i = 0; i < n; i++)  
        for(int j = 0; j < m; j++) 
            // Find maximum element in 
            // a matrix 
            if(maximum < mat[i][j]) 
                    maximum = mat[i][j]; 
  
    // Take 1-D array of (maximum + 1) 
    // size 
    int b[maximum + 1] = {0}; 
    for(int i = 0 ; i < n; i++) 
        for(int j = 0; j < m; j++) 
            b[mat[i][j]]++; 
  
    //print unique element 
    for(int i = 1; i <= maximum; i++) 
        if(b[i] == 1) 
            cout << i << " "; 
            flag = 1; 
              
    if(!flag){ 
        cout << "No unique element in the matrix"; 
    } 
} 
  
// Driver program 
int main() 
{ 
    int mat[R][C] = {{ 1, 2, 3, 20}, 
                     {5, 6, 20, 25}, 
                     {1, 3, 5, 6}, 
                     {6, 7, 8, 15}}; 
                       
    // function that calculate unique element 
    unique(mat, R, C); 
    return 0; 
} 
  
// This code is contributed by Naman_Garg. 

Java

// Java program to find unique 
// element in matrix 
class GFG 
{ 
static int R = 4, C = 4; 
  
// function that calculate  
// unique element 
static void unique(int mat[][],  
                   int n, int m) 
{ 
    int maximum = 0, flag = 0; 
    for(int i = 0; i < n; i++)  
        for(int j = 0; j < m; j++) 
          
            // Find maximum element  
            // in a matrix 
            if(maximum < mat[i][j]) 
                    maximum = mat[i][j]; 
  
    // Take 1-D array of  
    // (maximum + 1) size 
    int b[] = new int [maximum + 1]; 
    for(int i = 0 ; i < n; i++) 
        for(int j = 0; j < m; j++) 
            b[mat[i][j]]++; 
  
    //print unique element 
    for(int i = 1; i <= maximum; i++) 
        if(b[i] == 1) 
            System.out.print(i + " "); 
            flag = 1; 
              
    if(flag == 0) 
    { 
        System.out.println("No unique element " +  
                                "in the matrix"); 
    } 
} 
  
// Driver Code 
public static void main(String args[]) 
{ 
    int mat[][] = {{1, 2, 3, 20}, 
                   {5, 6, 20, 25}, 
                   {1, 3, 5, 6}, 
                   {6, 7, 8, 15}}; 
                      
    // function that calculate  
    // unique element 
    unique(mat, R, C); 
} 
} 
  
// This code is contributed 
// by Arnab Kundu 

Python3

# Python 3 program to find unique 
# element in matrix 
def unique(mat, n, m): 
  
    maximum = 0; flag = 0
      
    for i in range(0, n): 
        for j in range(0, m): 
              
            # Find maximum element in 
            # a matrix 
            if(maximum < mat[i][j]): 
                maximum = mat[i][j]; 
  
    uniqueElementDict = [0] * (maximum + 1) 
  
    # loops to traverse through the matrix  
    for i in range(0, n): 
        for j in range(0, m): 
                uniqueElementDict[mat[i][j]] += 1
  
    # Print all those keys whose count is 1 
    for key in range(maximum + 1): 
        if uniqueElementDict[key] == 1: 
            print (key, end = " ") 
            flag = 1
      
    if(flag == 0): 
        print("No unique element in the matrix") 
  
# Driver Code 
mat = [[1, 2, 3, 20],  
       [5, 6, 20, 25], 
       [1, 3, 5, 6], 
       [6, 7, 8, 15]] 
n = 4
m = 4
unique(mat, n, m) 

C#

// C# program to find unique  
// element in matrix 
using System; 
  
class GFG  
{  
static int R = 4, C = 4;  
  
// function that calculate  
// unique element  
static void unique(int [,]mat,  
                   int n, int m)  
{  
    int maximum = 0, flag = 0;  
    for(int i = 0; i < n; i++)  
        for(int j = 0; j < m; j++)  
          
            // Find maximum element  
            // in a matrix  
            if(maximum < mat[i, j])  
                    maximum = mat[i, j];  
  
    // Take 1-D array of  
    // (maximum + 1) size  
    int []b = new int [maximum + 1];  
    for(int i = 0 ; i < n; i++)  
        for(int j = 0; j < m; j++)  
            b[mat[i, j]]++;  
  
    // print unique element  
    for(int i = 1; i <= maximum; i++)  
        if(b[i] == 1)  
            Console.Write(i + " ");  
            flag = 1;  
              
    if(flag == 0)  
    {  
        Console.WriteLine("No unique element " +  
                               "in the matrix");  
    }  
}  
  
// Driver Code  
public static void Main()  
{  
    int [,]mat = {{1, 2, 3, 20},  
                  {5, 6, 20, 25},  
                  {1, 3, 5, 6},  
                  {6, 7, 8, 15}};  
                      
    // function that calculate  
    // unique element  
    unique(mat, R, C);  
}  
}  
  
// This code is contributed  
// by Subhadeep 

PHP

<?php 
// PHP program to find unique 
// element in matrix 
  
$R = 4; 
$C = 4; 
  
// function that calculate unique element 
function unique($mat, $n, $m) 
{ 
    $maximum = 0; 
    $flag = 0; 
    for($i = 0; $i < $n; $i++)  
        for($j = 0; $j < $m; $j++) 
          
            // Find maximum element in 
            // a matrix 
            if($maximum < $mat[$i][$j]) 
                    $maximum = $mat[$i][$j]; 
  
    // Take 1-D array of (maximum + 1) 
    // size 
    $b = array(); 
    for($j = 0; $j < $maximum + 1; $j++) 
        $b[$j] = 0; 
      
    for($i = 0 ; $i < $n; $i++) 
        for($j = 0; $j < $m; $j++) 
            $b[$mat[$i][$j]]++; 
  
    // print unique element 
    for($i = 1; $i <= $maximum; $i++) 
        if($b[$i] == 1) 
            echo "$i "; 
            $flag = 1; 
              
    if(!$flag) 
    { 
        echo "No unique element in the matrix"; 
    } 
} 
  
// Driver Code 
$mat = array(array(1, 2, 3, 20), 
             array(5, 6, 20, 25), 
             array(1, 3, 5, 6), 
             array(6, 7, 8, 15)); 
                  
// function that calculate unique element 
unique($mat, $R, $C); 
  
// This code is contributed by iAyushRaj 
?> 

Output:

2 7 8 25 15

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My Personal Notes

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

C++

Java

Python3

C#

PHP

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