1072. Flip Columns For Maximum Number of Equal Rows

Problem Link

Description

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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

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Python3

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())