Problem 2: Matrix Diagonal Sum (easy)

Problem Statement

Given a square matrix (2D array), calculate the sum of its two diagonals.

The two diagonals in consideration are the primary diagonal that spans from the top-left to the bottom-right and the secondary diagonal that spans from top-right to bottom-left. If a number is part of both diagonals (which occurs only for odd-sized matrices), it should be counted only once in the sum.

Examples

1. Example 1:

• Input:

[[1,2,3],
 [4,5,6],
 [7,8,9]]

• • Expected Output: 25
  • Justification: Summing up the two diagonals (1+5+9+3+7), we get 25. Please note that the element at [1][1] = 5 is counted only once.

1. Example 2:

• Input:

[[1,0],
 [0,1]]

• • Expected Output: 2
  • Justification: The sum of the two diagonals is 1+1 = 2.

1. Example 3:

• Input:

[[5]]

• • Expected Output: 5
  • Justification: Since there's only one element, it is the sum itself.

Constraints:

• n == mat.length == mat[i].length
• 1 <= n <= 100
• 1 <= mat[i][j] <= 100

Try it yourself