Flipping-an-Image

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题目地址

LeetCode#832 Flipping an Image

题目描述

  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

解题思路

  按照题目要求先 reverse 每一行，再取反即可

解题代码

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class Solution {
public:
    vector<vector<int>> flipAndInvertImage(vector<vector<int>> &A) {
        if (A.empty()) return A;
        vector<vector<int>> ret(A.size(), vector<int>(A[0].size(), 0));
        for (int i = 0; i < A.size(); ++i) {
            for (int j = A[i].size() - 1; j >= 0; --j) {
                ret[i][A[i].size() - j - 1] = !A[i][j];
            }
        }
        return ret;
    }
};
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