matrix-diagonal-sum

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Algorithms

Given a&nbsp;square&nbsp;matrix&nbsp;<code>mat</code>, 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.

&nbsp;
Example 1:
<img alt="" src="https://assets.leetcode.com/uploads/2020/08/14/sample_1911.png" style="width: 336px; height: 174px;" />
<pre>
Input: mat = [[1,2,3],
&nbsp; [4,5,6],
&nbsp; [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.
</pre>

Example 2:

<pre>
Input: mat = [[1,1,1,1],
&nbsp; [1,1,1,1],
&nbsp; [1,1,1,1],
&nbsp; [1,1,1,1]]
Output: 8
</pre>

Example 3:

<pre>
Input: mat = [[5]]
Output: 5
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>n == mat.length == mat[i].length</code></li>
	<li><code>1 &lt;= n &lt;= 100</code></li>
	<li><code>1 &lt;= mat[i][j] &lt;= 100</code></li>
</ul>

diagonalSum

Matrix Diagonal Sum

Check if Every Row and Column Contains All Numbers

check-if-every-row-and-column-contains-all-numbers

检查是否每一行每一列都包含全部整数

Check if Matrix Is X-Matrix

check-if-matrix-is-x-matrix

判断矩阵是否是一个 X 矩阵

Array

Matrix

给你一个正方形矩阵 <code>mat</code>，请你返回矩阵对角线元素的和。

请你返回在矩阵主对角线上的元素和副对角线上且不在主对角线上元素的和。

&nbsp;

示例&nbsp; 1：

<img alt="" src="https://assets.leetcode.com/uploads/2020/08/14/sample_1911.png" style="height:174px; width:336px" />

<pre>
输入：mat = [[1,2,3],
&nbsp; [4,5,6],
&nbsp; [7,8,9]]
输出：25
解释：对角线的和为：1 + 5 + 9 + 3 + 7 = 25
请注意，元素 mat[1][1] = 5 只会被计算一次。
</pre>

示例&nbsp; 2：

<pre>
输入：mat = [[1,1,1,1],
&nbsp; [1,1,1,1],
&nbsp; [1,1,1,1],
&nbsp; [1,1,1,1]]
输出：8
</pre>

示例 3：

<pre>
输入：mat = [[5]]
输出：5
</pre>

&nbsp;

提示：

<ul>
	<li><code>n == mat.length == mat[i].length</code></li>
	<li><code>1 &lt;= n &lt;= 100</code></li>
	<li><code>1 &lt;= mat[i][j] &lt;= 100</code></li>
</ul>