Weekly Challenge: The total array

Weekly Challenge 324

Each week Mohammad S. Anwar sends out The Weekly Challenge, a chance for all of us to come up with solutions to two weekly tasks. My solutions are written in Python first, and then converted to Perl. It's a great way for us all to practice some coding.

Challenge, My solutions

Task 1: 2D Array

Task

You are given an array of integers and two integers $r and $c.

Write a script to create two dimension array having $r rows and $c columns using the given array @ints.

My solution

For input from the command line, I take $rows and $cols as the last two values, the rest is @ints. In Python, this is achieved with the following line:

    *ints, rows, cols = array

Using Python's list comprehension, the solution is a single line after doing some sanity checks of the inputs.

def twod_array(ints: list, rows: int, cols: int) -> list[list[int]]:
    if rows < 1 or cols < 1:
        raise ValueError("Rows and columns must be greater than 0.")
    if rows * cols != len(ints):
        raise ValueError("The product of rows and columns must equal the length of the input list.")

    return [[ints[i * cols + j] for j in range(cols)] for i in range(rows)]

The Perl solution follows a more traditional approach.

sub main (@ints) {
    my $cols = pop @ints;
    my $rows = pop @ints;
    if ($rows < 1 or $cols < 1) {
        die "Rows and columns must be greater than 0.\n";
    }
    if (@ints != $rows * $cols) {
        die "The product of rows and columns must equal the length of the input list.\n";

    }
    my @result = ();
    foreach my $row (0 .. $rows - 1) {
        my @row = ();
        foreach my $col (0 .. $cols - 1) {
            push @row, shift @ints;
        }
        push @result, \@row;
    }

    say "(" . join(", ", map { '[' . join(", ", @$_) . ']'} @result) . ")";
}

Examples

$ ./ch-1.py 1 2 3 4 2 2
[[1, 2], [3, 4]]

$ ./ch-1.py 1 2 3 1 3
[[1, 2, 3]]

$ ./ch-1.py 1 2 3 4 4 1
[[1], [2], [3], [4]]

Task 2: Total XOR

Task

You are given an array of integers.

Write a script to return the sum of total XOR for every subset of given array.

My solution

For this task, I have an iterator i from 1 to the length of the list. For each iteration, I compute all possible combinations of this many items. Rather than reinventing a perfectly good wheel, I use the combinations function from itertools in Python, and from Algorithm::Combinatorics in Perl. For each combination, I calculate the XOR of all items.

def total_xor(ints: list) -> int:
    total = 0
    for i in range(1, len(ints) + 1):
        for combo in combinations(ints, i):
            xor_value = 0
            for num in combo:
                xor_value ^= num
            total += xor_value

    return total

Examples

$ ./ch-2.py 1 3
6

$ ./ch-2.py 5 1 6
28

$ ./ch-2.py 3 4 5 6 7 8
480

Simon Green @simongreennet