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2482. Maximum Rows Covered by Columns

My accepted Python solution to LeetCode problem 2482, Maximum Rows Covered by Columns, running in 4ms.

  • Difficulty: Medium
  • Python
  • Runtime 4ms
  • Memory 17.4MB

Read the problem on LeetCode View on GitHub

The problem statement is LeetCode’s and stays on their site. What follows is my accepted solution.

Python

Accepted on LeetCode — runtime 4ms, memory 17.4MB, accepted 2026-01-02.

python
class Solution:
    def maximumRows(self, matrix: List[List[int]], numSelect: int) -> int:
        from itertools import combinations
        
        m, n = len(matrix), len(matrix[0])
        
        # Convert each row to a bitmask
        row_masks = []
        for row in matrix:
            mask = 0
            for j, val in enumerate(row):
                if val == 1:
                    mask |= (1 << j)
            row_masks.append(mask)
        
        max_covered = 0
        
        # Try all combinations of numSelect columns
        for cols in combinations(range(n), numSelect):
            # Create column mask
            col_mask = 0
            for c in cols:
                col_mask |= (1 << c)
            
            # Count covered rows
            covered = 0
            for row_mask in row_masks:
                # Row is covered if all 1s in row are in selected columns
                if (row_mask & col_mask) == row_mask:
                    covered += 1
            
            max_covered = max(max_covered, covered)
        
        return max_covered

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