3239. Minimum Number of Flips to Make Binary Grid Palindromic I

Problem Link

Description

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You are given an m x n binary matrix grid.

A row or column is considered palindromic if its values read the same forward and backward.

You can flip any number of cells in grid from 0 to 1, or from 1 to 0.

Return the minimum number of cells that need to be flipped to make either all rows palindromic or all columns palindromic.

 

Example 1:

Input: grid = [[1,0,0],[0,0,0],[0,0,1]]

Output: 2

Explanation:

Flipping the highlighted cells makes all the rows palindromic.

Example 2:

Input: grid = [[0,1],[0,1],[0,0]]

Output: 1

Explanation:

Flipping the highlighted cell makes all the columns palindromic.

Example 3:

Input: grid = [[1],[0]]

Output: 0

Explanation:

All rows are already palindromic.

 

Constraints:

• m == grid.length
• n == grid[i].length
• 1 <= m * n <= 2 * 105
• 0 <= grid[i][j] <= 1

Solution

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Python3

class Solution:
    def minFlips(self, grid: List[List[int]]) -> int:
        rows, cols = len(grid), len(grid[0])
        res = 0
 
        # flip rows
        R = 0
        for row in grid:
            for j in range(cols // 2):
                if row[j] != row[~j]:
                    R += 1
        
        # flip cols
        C = 0
        for col in zip(*grid):
            for i in range(rows // 2):
                if col[i] != col[~i]:
                    C += 1
 
        return min(R, C)