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1072. Flip Columns For Maximum Number of Equal Rows

Difficulty Topics

Description

You are given an m x n binary matrix matrix.

You can choose any number of columns in the matrix and flip every cell in that column (i.e., Change the value of the cell from 0 to 1 or vice versa).

Return the maximum number of rows that have all values equal after some number of flips.

 

Example 1:

Input: matrix = [[0,1],[1,1]]
Output: 1
Explanation: After flipping no values, 1 row has all values equal.

Example 2:

Input: matrix = [[0,1],[1,0]]
Output: 2
Explanation: After flipping values in the first column, both rows have equal values.

Example 3:

Input: matrix = [[0,0,0],[0,0,1],[1,1,0]]
Output: 2
Explanation: After flipping values in the first two columns, the last two rows have equal values.

 

Constraints:

  • m == matrix.length
  • n == matrix[i].length
  • 1 <= m, n <= 300
  • matrix[i][j] is either 0 or 1.

Solution

flip-columns-for-maximum-number-of-equal-rows.py
class Solution:
    def maxEqualRowsAfterFlips(self, matrix: List[List[int]]) -> int:
        mp = collections.defaultdict(int)

        for r in matrix:
            A = []
            for c in r:
                A.append(r[0] ^ c)

            mp[tuple(A)] += 1

        return max(mp.values())