find-the-degree-of-each-vertex

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Algorithms

You are given a 2D integer array <code>matrix</code> of size <code>n x n</code> representing the adjacency matrix of an undirected graph with <code>n</code> vertices labeled from 0 to <code>n - 1</code>.

<ul>
	<li><code>matrix[i][j] = 1</code> indicates that there is an edge between vertices <code>i</code> and <code>j</code>.</li>
	<li><code>matrix[i][j] = 0</code> indicates that there is no edge between vertices <code>i</code> and <code>j</code>.</li>
</ul>

The degree of a vertex is the number of edges connected to it.

Return an integer array <code>ans</code> of size <code>n</code> where <code>ans[i]</code> represents the degree of vertex <code>i</code>.

&nbsp;
Example 1:

<img alt="" src="https://assets.leetcode.com/uploads/2026/03/14/g41f.png" style="width: 180px; height: 142px;" />

<div class="example-block">
Input: matrix = [[0,1,1],[1,0,1],[1,1,0]]

Output: [2,2,2]

Explanation:

<ul>
	<li>Vertex 0 is connected to vertices 1 and 2, so its degree is 2.</li>
	<li>Vertex 1 is connected to vertices 0 and 2, so its degree is 2.</li>
	<li>Vertex 2 is connected to vertices 0 and 1, so its degree is 2.</li>
</ul>

Thus, the answer is <code>[2, 2, 2]</code>.
</div>

Example 2:

<img alt="" src="https://assets.leetcode.com/uploads/2026/03/14/g42f.png" style="width: 180px; height: 145px;" />

<div class="example-block">
Input: matrix = [[0,1,0],[1,0,0],[0,0,0]]

Output: [1,1,0]

Explanation:

<ul>
	<li>Vertex 0 is connected to vertex 1, so its degree is 1.</li>
	<li>Vertex 1 is connected to vertex 0, so its degree is 1.</li>
	<li>Vertex 2 is not connected to any vertex, so its degree is 0.</li>
</ul>

Thus, the answer is <code>[1, 1, 0]</code>.
</div>

Example 3:

<div class="example-block">
Input: matrix = [[0]]

Output: [0]

Explanation:

There is only one vertex and it has no edges connected to it. Thus, the answer is <code data-end="1156" data-start="1151">[0]</code>.
</div>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= n == matrix.length == matrix[i].length &lt;= 100</code>​​​​​​​</li>
	<li><code>​​​​​​​matrix[i][i] == 0</code></li>
	<li><code>matrix[i][j]</code> is either 0 or 1</li>
	<li><code>matrix[i][j] == matrix[j][i]</code></li>
</ul>

第 497 场周赛

weekly-contest-497

findDegrees

中级工程师

Find the Degree of Each Vertex

Graph

Array

Matrix

给你一个大小为 <code>n x n</code> 的二维整数数组 <code>matrix</code>，以邻接矩阵形式表示一个&nbsp;无向图。该图包含 <code>n</code> 个顶点，编号从 0 到 <code>n - 1</code>。

<ul>
	<li><code>matrix[i][j] = 1</code> 表示顶点 <code>i</code> 与顶点 <code>j</code> 之间存在一条边。</li>
	<li><code>matrix[i][j] = 0</code> 表示顶点 <code>i</code> 与顶点 <code>j</code> 之间不存在边。</li>
</ul>

顶点的&nbsp;度（degree）定义为与该顶点相连的边的数量。

请返回一个长度为 <code>n</code> 的整数数组 <code>ans</code>，其中 <code>ans[i]</code> 表示顶点 <code>i</code> 的度。

&nbsp;

示例 1：

<img alt="" src="https://assets.leetcode.com/uploads/2026/03/14/g41f.png" style="width: 180px; height: 142px;" />

<div class="example-block">
输入： matrix = [[0,1,1],[1,0,1],[1,1,0]]

输出： [2,2,2]

解释：

<ul>
	<li>顶点 0 与顶点 1 和 2 相连，因此其度为 2。</li>
	<li>顶点 1 与顶点 0 和 2 相连，因此其度为 2。</li>
	<li>顶点 2 与顶点 0 和 1 相连，因此其度为 2。</li>
</ul>

因此，答案为 <code>[2, 2, 2]</code>。
</div>

示例 2：

<img alt="" src="https://assets.leetcode.com/uploads/2026/03/14/g42f.png" style="width: 180px; height: 145px;" />

<div class="example-block">
输入： matrix = [[0,1,0],[1,0,0],[0,0,0]]

输出： [1,1,0]

解释：

<ul>
	<li>顶点 0 与顶点 1 相连，因此其度为 1。</li>
	<li>顶点 1 与顶点 0 相连，因此其度为 1。</li>
	<li>顶点 2 没有与任何顶点相连，因此其度为 0。</li>
</ul>

因此，答案为 <code>[1, 1, 0]</code>。
</div>

示例 3：

<div class="example-block">
输入： matrix = [[0]]

输出： [0]

解释：

图中只有一个顶点，且没有任何边与其相连，因此答案为 <code>[0]</code>。
</div>

&nbsp;

提示：

<ul>
	<li><code>1 &lt;= n == matrix.length == matrix[i].length &lt;= 100</code></li>
	<li><code>matrix[i][i] == 0</code></li>
	<li><code>matrix[i][j]</code> 仅为 0 或 1</li>
	<li><code>matrix[i][j] == matrix[j][i]</code></li>
</ul>