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Java solution for finding the transpose of a matrix

Introduction

A transpose of a matrix is a new matrix formed by exchanging rows with columns. In this leetcode problem, we will find the transpose of a 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]]

Solution

• If the input matrix is of size ROW, COL then the Transpose matrix would be of size of ROW=COL & COL=ROW.
• The location of elements in the transpose matrix will be inverted as well, which means if the element in the input matrix is at i, j then in the transpose matrix it would be j, i.
  so, transpose[col][row]=matrix[row][col]

class Solution {
    public int[][] transpose(int[][] matrix) {
        int rows = matrix.length;
        int cols = matrix[0].length;
        int[][] res = new int[cols][rows];

        for(int i=0;i<rows;i++){
            for(int j=0;j<cols;j++){
                res[j][i]=matrix[i][j];
            }
        }

        return res;
    }
}

Results

• Our solution is accepted and it’s pretty efficient.

Complexity

Time complexity:
time complexity is O(N²) since we are iterating over each element.

Space complexity:
space complexity is O(N), and N is the size of the input matrix for the result matrix.

Conclusion

In this problem, we learned about the 2D matrix and the transpose of a matrix. Time complexity is O(N²) and space complexity is O(N).

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