[LeetCode] 832. Flipping an Image

Description

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:

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:

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

Analyse

给定一个二元矩阵A，先横向 flip，再 invert，返回结果矩阵

flip 翻转 [1, 1, 0] -> [0, 1, 1]
invert 反转 [1, 1, 0] -> [0, 0, 1]

逆向读矩阵的每一行，invert后插入矩阵

vector<vector<int>> flipAndInvertImage(vector<vector<int>>& A) {
    vector<vector<int>> result;
    for (vector<vector<int>>::iterator iter = A.begin(); iter != A.end(); iter++)
    {
        vector<int> line;
        for (vector<int>::reverse_iterator inner_iter = iter->rbegin(); inner_iter != iter->rend(); inner_iter++)
        {
            int a = (*inner_iter);
            line.push_back((a == 0)? 1 : 0);
        }
        result.push_back(line);
        cout << endl;
    }
    return result;
}