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 0indexed).
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 either0
or1
.

