leetcode-832-Flipping-an-Image

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描述

Given a binary matrix A, we want to flip the image horizontally, then invert it, and return the resulting image.

To flip an image horizontally means that each row of the image is reversed. For example, flipping [1, 1, 0] horizontally results in [0, 1, 1].

To invert an image means that each 0 is replaced by 1, and each 1 is replaced by 0. For example, inverting [0, 1, 1] results in [1, 0, 0].

Example 1:

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Input: [[1,1,0],[1,0,1],[0,0,0]]
Output: [[1,0,0],[0,1,0],[1,1,1]]
Explanation: First reverse each row: [[0,1,1],[1,0,1],[0,0,0]].
Then, invert the image: [[1,0,0],[0,1,0],[1,1,1]]

Example 2:

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Input: [[1,1,0,0],[1,0,0,1],[0,1,1,1],[1,0,1,0]]
Output: [[1,1,0,0],[0,1,1,0],[0,0,0,1],[1,0,1,0]]
Explanation: First reverse each row: [[0,0,1,1],[1,0,0,1],[1,1,1,0],[0,1,0,1]].
Then invert the image: [[1,1,0,0],[0,1,1,0],[0,0,0,1],[1,0,1,0]]

Notes:

  • 1 <= A.length = A[0].length <= 20
  • 0 <= A[i][j] <= 1

分析

给定一个矩阵，左右对称交换值，并且值要进行翻转（与1进行异或运算），一次循环即可。时间复杂度是 $O(n^2)$

解决方案1(Java)

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class Solution {
    public int[][] flipAndInvertImage(int[][] A) {
        int mid = A[0].length;
        for (int[] row: A) {
            for (int i = 0; i < (mid+1)/2; i++) {
                int tmp = row[i] ^ 1;
                row[i] = row[mid-i-1] ^ 1;
                row[mid-i-1] = tmp;
            }
        }
        return A;
    }
}

题目来源