1582 Special Positions in a Binary Matrix

Given an m x n binary matrix mat, 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:

1 0 0
0 0[1]
1 0 0

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:

[1]0 0
 0[1]0
 0 0[1]

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

Constraints:

• m == mat.length
• n == mat[i].length
• 1 <= m, n <= 100
• mat[i][j] is either 0 or 1.

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class Solution:
    def numSpecial(self, mat: List[List[int]]) -> int:
        row_sums = [sum(r) for r in mat]
        col_sums = [sum([r[i] for r in mat]) for i in range(len(mat[0]))]
        res = 0
        for i in range(len(mat)):
            for j in range(len(mat[0])):
                if mat[i][j] == 1 and row_sums[i] == 1 and col_sums[j] == 1:
                    res += 1
        return res