LeetCode 1572. Matrix Diagonal Sum

Question

Given a square matrix mat, return the sum of the matrix diagonals.

Only include the sum of all the elements on the primary diagonal and all the elements on the secondary diagonal that are not part of the primary diagonal.

 

Example 1:

Input: mat = [[1,2,3],
            [4,5,6],
            [7,8,9]]
Output: 25
Explanation: Diagonals sum: 1 + 5 + 9 + 3 + 7 = 25
Notice that element mat[1][1] = 5 is counted only once.

 

Example 2:

Input: mat = [[1,1,1,1],
              [1,1,1,1],
              [1,1,1,1],
              [1,1,1,1]]
Output: 8

 

Example 3:

Input: mat = [[5]]
Output: 5

 

Constraints:

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

 

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Solution

Python

class Solution:
    def diagonalSum(self, mat: List[List[int]]) -> int:
        sum =sum1 =sum2 = 0
        for row in range(len(mat)):
            for column in range(len(mat[row])):
                if row == column:
                    print(row, column)
                    sum1 += mat[row][column]
                if row + column == len(mat) -1:
                    print(row, column)
                    sum2 += mat[row][column]
        if len(mat) % 2 == 1:
            sum = sum1 + sum2 - mat[int(len(mat)/2)][int(len(mat)/2)]
        else:
            sum = sum1 + sum2
            
        return sum

Java