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# 1582. Special Positions in a Binary Matrix

<https://leetcode.com/problems/special-positions-in-a-binary-matrix>

## Description

Given a `rows x cols` matrix `mat`, where `mat[i][j]` is either `0` or `1`, return *the number of special positions in `mat`.*

A position `(i,j)` is called **special** if `mat[i][j] == 1` and all other elements in row `i` and column `j` are `0` (rows and columns are **0-indexed**).

**Example 1:**

```
**Input:** mat = [[1,0,0],
              [0,0,**1**],
              [1,0,0]]
**Output:** 1
**Explanation:** (1,2) is a special position because mat[1][2] == 1 and all other elements in row 1 and column 2 are 0.
```

**Example 2:**

```
**Input:** mat = [[**1**,0,0],
              [0,**1**,0],
              [0,0,**1**]]
**Output:** 3
**Explanation:** (0,0), (1,1) and (2,2) are special positions. 
```

**Example 3:**

```
**Input:** mat = [[0,0,0,**1**],
              [**1**,0,0,0],
              [0,1,1,0],
              [0,0,0,0]]
**Output:** 2
```

**Example 4:**

```
**Input:** mat = [[0,0,0,0,0],
              [**1**,0,0,0,0],
              [0,**1**,0,0,0],
              [0,0,**1**,0,0],
              [0,0,0,1,1]]
**Output:** 3
```

**Constraints:**

* `rows == mat.length`
* `cols == mat[i].length`
* `1 <= rows, cols <= 100`
* `mat[i][j]` is `0` or `1`.

## ac

```java
```