[Coding Challenge] Special Elements in Matrix

This coding challenge was asked in Goldman Sachs coderpad coding interview round and also in the Syntel hackathon interview.

Problem Statement: Special Elements in Matrix

Given a matrix of size m*n, m denotes the row starting with index 0 and n denotes the column starting with index 0.

The matrix will hold distinct integers as elements.

We need to find a distinct number of positional elements which are either the minimum or maximum in their corresponding row or column.

Please return -1 if any row or any column has multiple minimum or maximum elements.

For example, given a matrix of size 3*3, the elements are stored as follows.

1  3  4
5  2  9
8  7  6

The expected output is 7.

In the above example, we identified the output as 7 based on below.

1 - minimum in row and column
4 - Maximum in row
2 - Minimum in column and row
9 - Maximum in row and column
8 - Maximum in row and column
7 - Maximum in column
6 - Minimum in row

Input:

m - integer - number of rows
n - integer - number of columns
m * n matrix

Output:

r - integer - result

Constraints:

0<m,n<100
Elements in the matrix are positive integers.

Programming Solution in Python:

Here is the code for special elements in matrix solved in Python.

# Complete the countSpecialElements function below.
  
def countSpecialElements(matrix):
  nRows= len(matrix)
  nCount=0
  
  for row in matrix:
    for indexCol, element in enumerate(row):
  
      if element==min(row) or element==max(row):
        if row.count(element)>1:
          return -1
        nCount=nCount+1
  
      else:
        listColumn=[]
  
        for indexRow in range(0, nRows):
          listColumn.append(matrix[indexRow][indexCol])
  
        if element==min(listColumn) or element==max(listColumn):
          if listColumn.count(element)>1:
            return -1
          nCount=nCount+1

  return nCount
  
if __name__ == '__main__':
  nCount = countSpecialElements([[1, 3, 4],[5, 2, 9],[8, 7, 6]])
  print(nCount)

Output:

7

In Python, matrix elements are stored as a nested list. To solve this kind of problem, you should have a good understanding of the list and its methods.

If you are solving this coding question in a competitive test round, consider all boundary cases.

There was one more question was asked in the Goldman Sachs coding round- Secure My Conversation.

Aniruddha Chaudhari

I am a Python enthusiast who loves Linux and Vim. I hold a Master of Computer Science degree from NIT Trichy and have 10 years of experience in the IT industry, focusing on the Software Development Lifecycle from Requirements Gathering, Design, Development to Deployment. I have worked at IBM, Ericsson, and NetApp, and I share my knowledge on CSEstack.org.