[HackerRank] Diagonal Difference

Interview Preparation Kits > 1 Week Preparation Kit > Day 2 > Diagonal Difference

 

Given a square matrix, calculate the absolute difference between the sums of its diagonals.

For example, the square matrix arr is shown below:

1 2 3
4 5 6
9 8 9

The left-to-right diagonal = 1 + 5 + 9 = 15. The right to left diagonal = 3 + 5 + 9 = 17. Their absolute difference is |15 - 17| = 2.

 

Function description

Complete the diagonalDifference function in the editor below.

diagonalDifference takes the following parameter:

• int arr[n][m]: an array of integers

 

Return

• int: the absolute diagonal difference

 

Input Format

The first line contains a single integer, n, the number of rows and columns in the square matrix arr.

Each of the next n lines describes a row, arr[i], and consists of n space-separated integers -100 < arr[i][j] <= 100.

 

Constraints

 

Output Format

Return the absolute difference between the sums of the matrix's two diagonals as a single integer.

 

Sample Input

3 11 2 4 4 5 6 10 8 -12

 

Sample Output

15

 

Explanation

The primary diagonal is:

11
   5
     -12

 

Sum across the primary diagonal: 11 + 5 - 12 = 4

 

The secondary diagonal is:

     4
   5
10

 

Sum across the secondary diagonal: 4 + 5 + 10 = 19

Difference: |4 - 19| = 15

Note: |x| is the absolute value of x

 

---

#!/bin/python3

import math
import os
import random
import re
import sys

#
# Complete the 'diagonalDifference' function below.
#
# The function is expected to return an INTEGER.
# The function accepts 2D_INTEGER_ARRAY arr as parameter.
#
'''
3
11 2 4
4 5 6
10 8 -12
'''
def diagonalDifference(arr):
    # Write your code here
    dig = 0
    anti_dig = 0
    l = len(arr[0])

    for i in range(l):
        dig += arr[i][i]
        anti_dig += arr[i][(l-1)-i]

    return abs(dig-anti_dig)

if __name__ == '__main__':
    # fptr = open(os.environ['OUTPUT_PATH'], 'w')

    n = int(input().strip())

    arr = []

    for _ in range(n):
        arr.append(list(map(int, input().rstrip().split())))

    result = diagonalDifference(arr)
    print(result)

    # fptr.write(str(result) + '\n')
    #
    # fptr.close()