# ---
# title: 1572. Matrix Diagonal Sum
# id: problem1572
# author: Tian Jun
# date: 2020-10-31
# difficulty: Easy
# categories: Array
# link: <https://leetcode.com/problems/matrix-diagonal-sum/description/>
# hidden: true
# ---
# 
# 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:**
# 
# ![](https://assets.leetcode.com/uploads/2020/08/14/sample_1911.png)
# 
#     
#     
#     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`
# 
# 
## @lc code=start
using LeetCode

## add your code here:
## @lc code=end
