Special Positions in a Binary Matrix
Given an M x N binary matrix
mat, return the number of special positions in the matrix. A position (i, j) is defined as 'special' if mat[i][j] == 1 and all other elements in the i-th row and j-th column are 0 (i.e., it is the only 1 in its respective row and column). Constraints: m == mat.length n == mat[i].length 1 <= m, n <= 500 mat[i][j] is either 0 or 1.JavaFrequency CountingTwo-Pass Matrix Scan
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