Solution for Advent of Code 2016 - Day 6: Signals and Noise

Link to the puzzle text

Part 1

In this puzzle, we are asked to password hidden in columns of text. Each column has a most commonly used letter. Concatenating these together for each column gives us the solution.

First we transpose our text from row-oriented to column-oriented:

columns = []
for i in range(len(lines[0])):
    columns.append([line[i] for line in lines])

We then iterate over the columns, use the python Counter class to find the most common letter and concatenate them together:

def most_common(columns, position):
    solution = ""
    for column in columns:
        c = Counter(column)
        char = c.most_common()[position][0]
        solution += char
    return solution

Part 2

In part two, the password is found by concatenating the least commonly used letter in each column.

We reuse the function from part 1, supply the argument -1 for the position instead. In python this yields the last element of a list. The rest of the function works the same and results in the password.

Link to my solutions