867. Transpose Matrix

Problem

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.

  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]]

  Constraints:

• m == matrix.length

• n == matrix[i].length

• 1 <= m, n <= 1000

• 1 <= m * n <= 10^5

• -10^9 <= matrix[i][j] <= 10^9

Solution (Java)

class Solution {
    public int[][] transpose(int[][] input) {
        int[][] output = new int[input[0].length][input.length];
        for (int i = 0, b = 0; i < input.length; i++, b++) {
            for (int j = 0, a = 0; j < input[0].length; j++, a++) {
                output[a][b] = input[i][j];
            }
        }
        return output;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).