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

Easy題目就不細(xì)說了。

Runtime:?0 ms, faster than?100.00%?of?Java?online submissions for?Matrix Diagonal Sum.

Memory Usage:?42.3 MB, less than?70.06%?of?Java?online submissions for?Matrix Diagonal Sum.