Given a n x n matrix. The problem is to find all the distinct elements common to all rows of the matrix. The elements can be printed in any order.

Examples:

Input : mat[][] = {  {2, 1, 4, 3},
                     {1, 2, 3, 2},  
                     {3, 6, 2, 3},  
                     {5, 2, 5, 3}  }
Output : 2 3

Input : mat[][] = {  {12, 1, 14, 3, 16},
                     {14, 2, 1, 3, 35},  
                     {14, 1, 14, 3, 11},  
                     {14, 25, 3, 2, 1},
                     {1, 18, 3, 21, 14}  }
Output : 1 3 14

Python Solution

def common_elements(matrix): 
  # declare dictionary and result array
  keys = {} 
  results = [] 
  
  #initialize dictionary with null list values
  for i in range(0, len(matrix)): 
    for j in range(0, len(matrix[i])): 
      if matrix[i][j] not in keys: 
        keys[matrix[i][j]] = []
  
  # update matrix[row][col] array with values
  for i in range(0, len(matrix)): 
    for j in range(0, len(matrix[i])): 
      if i not in keys[matrix[i][j]]:
        keys[matrix[i][j]].append(i)
  
  # if length of value of key is equal to matrix length add it to result
  for key in keys: 
      if len(keys[key]) == len(matrix):
        results.append(key)

  return results      
    
matrix =   [[2, 1, 4, 3],
          [1, 2, 3, 2], 
          [3, 6, 2, 3],    
          [5, 2, 5, 3]]
          
print(common_elements(matrix))

Source – Geekforgeeks

Code – Github