[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
m - integer - number of rows n - integer - number of columns m * n matrix
r - integer - result
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)
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.
The output of your code is 10, not 9.
Edited. Thanks for the correction, Ravi!
Sir, there is a mistake in code…of indentation inside else block…
the correct output is 7.
Thanks for the correction, Moksha! Indentation is fixed.
Is there a more efficient way to solve this problem? Because at worst this code is using a triple nested for loop.
One question is when will the -1 if any row or any column has multiple minimum or maximum elements occur. Since it is mentioned in the problem statement that The matrix will hold distinct integers as elements.