Java List Transpose transpose(List> matrix)

Description

Transposes a given matrix represented as a list of lists.

License

Open Source License

Parameter

Parameter	Description
T	the type of matrix elements
matrix	the matrix to be transposed

Return

the transposed matrix

Declaration

public static <T> List<List<T>> transpose(List<List<T>> matrix) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

import java.util.ArrayList;

import java.util.List;

public class Main {
    /**/*from w ww.j a  v a 2 s . co m*/
     * Transposes a given matrix represented as a list of lists.
     * 
     * @param <T>
     *            the type of matrix elements
     * @param matrix
     *            the matrix to be transposed
     * @return the transposed matrix
     */
    public static <T> List<List<T>> transpose(List<List<T>> matrix) {
        List<List<T>> transposedMatrix = new ArrayList<List<T>>();

        int nbOfColumns = -1;
        int nbOfRows = -1;

        // Check if the given list of lists represents a proper matrix, i.e., each row has to feature an equal number of
        // columns
        if (matrix != null && !matrix.isEmpty()) {
            nbOfRows = matrix.size();

            for (List<T> row : matrix) {
                if (nbOfColumns == -1)
                    nbOfColumns = row.size();
                else if (nbOfColumns != row.size())
                    throw new IllegalArgumentException("The given list of lists is not a proper matrix.");
            }
        }

        // transpose the matrix
        for (int i = 0; i < nbOfColumns; i++) {
            List<T> newRow = new ArrayList<T>(nbOfRows);

            for (List<T> row : matrix) {
                newRow.add(row.get(i));
            }

            transposedMatrix.add(newRow);
        }

        return transposedMatrix;
    }
}

Related

1. transpose(List> input)
2. transpose(List> matrix)
3. transpose(List> table)