1072. Flip columns for maximum number of equal rows

//1072. Flip columns for maximum number of equal rows

class Solution {
    public int maxEqualRowsAfterFlips(int[][] matrix) {
        int n = matrix.length, m = matrix[0].length, res = 0;
        Map<Integer, Integer> map = new HashMap<>();

        for(int i = 0; i < n; i++) {
            if(matrix[i][m - 1] == 1) {
                for(int j = 0; j < m; j++) {
                    matrix[i][j] ^= matrix[i][m - 1];
                }
            }

            res = Math.max(res, map.merge(Arrays.hashCode(matrix[i]), 1, Integer::sum));
        }
        
        return res;
    }
}