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leetcode-problemset/leetcode-cn/problem (Chinese)/元素和为目标值的子矩阵数量 [number-of-submatrices-that-sum-to-target].html
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<p>给出矩阵 <code>matrix</code> 和目标值 <code>target</code>,返回元素总和等于目标值的非空子矩阵的数量。</p>
<p>子矩阵 <code>x1, y1, x2, y2</code> 是满足 <code>x1 <= x <= x2</code> 且 <code>y1 <= y <= y2</code> 的所有单元 <code>matrix[x][y]</code> 的集合。</p>
<p>如果 <code>(x1, y1, x2, y2)</code> 和 <code>(x1', y1', x2', y2')</code> 两个子矩阵中部分坐标不同(如:<code>x1 != x1'</code>),那么这两个子矩阵也不同。</p>
<p> </p>
<p><strong>示例 1</strong></p>
<p><img alt="" src="https://assets.leetcode.com/uploads/2020/09/02/mate1.jpg" style="width: 242px; height: 242px;" /></p>
<pre>
<strong>输入:</strong>matrix = [[0,1,0],[1,1,1],[0,1,0]], target = 0
<strong>输出:</strong>4
<strong>解释:</strong>四个只含 0 的 1x1 子矩阵。
</pre>
<p><strong>示例 2</strong></p>
<pre>
<strong>输入:</strong>matrix = [[1,-1],[-1,1]], target = 0
<strong>输出:</strong>5
<strong>解释:</strong>两个 1x2 子矩阵,加上两个 2x1 子矩阵,再加上一个 2x2 子矩阵。
</pre>
<p><strong>示例 3</strong></p>
<pre>
<strong>输入:</strong>matrix = [[904]], target = 0
<strong>输出:</strong>0
</pre>
<p> </p>
<p><strong><strong>提示:</strong></strong></p>
<ul>
<li><code>1 <= matrix.length <= 100</code></li>
<li><code>1 <= matrix[0].length <= 100</code></li>
<li><code>-1000 <= matrix[i] <= 1000</code></li>
<li><code>-10^8 <= target <= 10^8</code></li>
</ul>