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.

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