<p>Given an <code>m x n</code> binary matrix <code>mat</code>, return <em>the number of special positions in </em><code>mat</code><em>.</em></p>

<p>A position <code>(i, j)</code> is called <strong>special</strong> if <code>mat[i][j] == 1</code> and all other elements in row <code>i</code> and column <code>j</code> are <code>0</code> (rows and columns are <strong>0-indexed</strong>).</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/12/23/special1.jpg" style="width: 244px; height: 245px;" />
<pre>
<strong>Input:</strong> mat = [[1,0,0],[0,0,1],[1,0,0]]
<strong>Output:</strong> 1
<strong>Explanation:</strong> (1, 2) is a special position because mat[1][2] == 1 and all other elements in row 1 and column 2 are 0.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/12/24/special-grid.jpg" style="width: 244px; height: 245px;" />
<pre>
<strong>Input:</strong> mat = [[1,0,0],[0,1,0],[0,0,1]]
<strong>Output:</strong> 3
<strong>Explanation:</strong> (0, 0), (1, 1) and (2, 2) are special positions.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

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

class Solution {
public:
    int numSpecial(vector<vector<int>>& mat) {
        int rows = mat.size();
        int cols = mat[0].size();

        int special = 0;

        unordered_map<int,int> vis_rows;
        unordered_map<int,int> vis_cols;

        for (int i = 0; i < rows; i++)
        {
            for (int j = 0; j < cols; j++)
            {
                if (mat[i][j]==1)
                {
                    vis_rows[i]++;
                    vis_cols[j]++;
                }
            }
        }

        for (int i = 0; i < rows; i++)
        {
            for (int j = 0; j < cols; j++)
            {
                if (vis_rows.find(i)!=vis_rows.end() && vis_cols.find(j)!=vis_cols.end())
                {
                    if (vis_rows[i] == 1 and vis_cols[j]==1)
                    {
                        if (mat[i][j]==1)
                            special++;
                    }
                }
            }
        }

        return special;
        
    }
};
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