867. Transpose Matrix

2021, Feb 25 One min read

1. Description

Given a 2D integer array matrix, return the transpose of matrix.
The transpose of a matrix is the matrix flipped over its main diagonal, switching the matrix’s row and column indices.

2. Example

Example 1

Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
Output: [[1,4,7],[2,5,8],[3,6,9]]

Example 2

Input: matrix = [[1,2,3],[4,5,6]]
Output: [[1,4],[2,5],[3,6]]

3. Constraints

m == matrix.length
n == matrix[i].length
1 <= m, n <= 1000
1 <= m * n <= 10$^{5}$
-10$^{9}$ <= matrix[i][j] <= 10$^{9}$

4. Solutions

Queue

n = i_matrix.size() * i_matrix.front().size()
Time complexity: O(n)
Space complexity: O(n)

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class Solution
{
public:
    // vector<vector<int>> transpose(vector<vector<int>>& matrix)
    vector<vector<int>> transpose(const vector<vector<int>> &i_matrix)
    {
        const int rows = i_matrix.size();
        const int columns = i_matrix.front().size();

        vector<vector<int>> invertedMatrix(columns, vector<int>(rows));

        for(int row = 0; row < rows; row++)
        {
            for(int column = 0; column < columns; column++)
            {
                invertedMatrix[column][row] = i_matrix[row][column];
            }
        }

        return invertedMatrix;
    }
};

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