from utils import *
from collections import Counter

def only_choice(values):
    """Finalize all values that are the only choice for a unit.

    Go through all the units, and whenever there is a unit with a value
    that only fits in one box, assign the value to this box.

    Input: Sudoku in dictionary form.
    Output: Resulting Sudoku in dictionary form after filling in only choices.
    """
    # TODO: Implement only choice strategy here
    # display(values)
    for unit in unitlist:
        c = Counter()
        for box in unit:
            c.update(values[box])
        for box in unit:
            for value in values[box]:
                if c[value] == 1 and len(values[box]) > 1:
                    values[box] = value
    return values