Arrays - Transpose Matrix

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

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

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 <= 10⁵
-10⁹ <= matrix[i][j] <= 10⁹

Solution 1 - Convert rows to columns

In this approach, we will simply convert rows to columns.

Implementation steps:

Create a variable result 2D array with rows length as columns length input array, and columns length as rows length input array.
Then, loop through for each row i and column j of input array matrix, add the value to row j and column i of result array.

import java.util.Arrays; import java.util.stream.Stream; public class TransposeMatrix { static int[][] transposeMatrix(int[][] matrix) { if(matrix == null) { return null; } int[][] result = new int[matrix[0].length][matrix.length]; for(int i=0; i<matrix.length; i++) { for(int j=0; j<matrix[i].length; j++) { result[j][i] = matrix[i][j]; } } return result; } public static void main(String[] args) { int[][] result = transposeMatrix(new int[][] {{1,2}}); Stream.of(result).forEach(row->System.out.println(Arrays.toString(row))); result = transposeMatrix(new int[][] {{1,2}, {3,4}, {5,6}}); Stream.of(result).forEach(row->System.out.println(Arrays.toString(row))); result = transposeMatrix(new int[][] {{}}); Stream.of(result).forEach(row->System.out.println(Arrays.toString(row))); } }

Complexity Analysis:

Time complexity: Above code runs in O(m * n) time where m is rows length, and n is columns length of input array matrix.
Space complexity: O(m * n) for the result array.

Above implementations source code can be found at GitHub link for Java code

Constraints:

Contents

Implementation steps:

Complexity Analysis: