LeetCode知识点总结 - 861

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于 2024-01-14 17:53:15 发布

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分类专栏： LeetCode 文章标签： leetcode 算法职场和发展

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这篇文章讨论了解题思路，如何在给定的二进制矩阵中通过翻转行或列来最大化得分。关键在于确定每个列中0的数量，优先选择能增加最高位（MSB）为1的行进行翻转操作。Solution类提供了实现方法。

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LeetCode 861. Score After Flipping Matrix

考点	难度
Greedy	Easy

题目

You are given an m x n binary matrix grid.

A move consists of choosing any row or column and toggling each value in that row or column (i.e., changing all 0’s to 1’s, and all 1’s to 0’s).

Every row of the matrix is interpreted as a binary number, and the score of the matrix is the sum of these numbers.

Return the highest possible score after making any number of moves (including zero moves).

思路

先判断most significant bit（A[i][0]）是不是1，如果不是需要flip。之后对每一个column数1和0的个数（需要考虑msb被flip过）如果0的个数更少需要flip。

答案

class Solution(object):
    def matrixScore(self, A):
        M, N = len(A), len(A[0])
        res = (1 << N - 1) * M
        for j in range(1, N):
            cur = sum(A[i][j] == A[i][0] for i in range(M))
            res += max(cur, M - cur) * (1 << N - 1 - j)
        return res