Python program to find Matrix Diagonal Difference

Program Statement – Matrix Diagonal Difference
You are given a square matrix of size N×N. Can you calculate the absolute difference of the sums across the main diagonal and the secondary diagonal?
https://www.hackerrank.com/challenges/diagonal-difference

Program – Python 3 Version

mat = []

nrow = int(input())

for i in range(nrow):

  mat.extend(list(map(int,input().split()))) #keep extending the array

#Main Diagonal Sum

indx,pd_sum = 0,0

for i in range(nrow):

  pd_sum += mat[indx]

  indx += nrow + 1

#Secondary Diagonal Sum

indx,sd_sum = nrow-1,0

for i in range(nrow):

  sd_sum += mat[indx]

  indx += nrow - 1

print(abs(pd_sum – sd_sum))

Input -

3
11 2 4
4 5 6
10 8 -12

Output - 15