YouTube coding task solution just for fun

unit_converter.py

# The task is got form this video: https://www.youtube.com/watch?v=V8DGdPkBBxg

from typing import Mapping, Set, Sequence, Tuple, Union

input_facts = (
    "m = 3.28 ft",
    "ft = 12 in",
    "hr = 60 min",
    "min = 60 sec",
)

input_queries = (
    "2 m = ? in",
    "13 in = ? m",
    "13 in = ? hr",
)

def parse_facts(*facts: str) -> Sequence[Tuple[str, str, float]]:
    out = []
    
    for fact in facts:
        unit_a, coef__unit_b = fact.split(' = ')
        coef, unit_b = coef__unit_b.split()
        out.append((unit_a, unit_b, float(coef)))
    
    return out

def parse_queries(*queries: str) -> Sequence[Tuple[float, str, str]]:
    out = []
    
    for query in queries:
        value, unit_from__unit_to = query.split(' ', 1)
        unit_from, unit_to = unit_from__unit_to.split(' = ? ')
        out.append((float(value), unit_from, unit_to))
    
    return out
    
def make_conversion_matrix(*facts: Tuple[str, str, float]) -> Mapping[str, Mapping[str, float]]:
    mat = dict()
    
    for fact in facts:
        forward = mat.get(fact[0], dict())
        forward.update({fact[1]: fact[2]})
        
        backward = mat.get(fact[1], dict())
        backward.update({fact[0]: 1/fact[2]})
        
        mat.update({
            fact[0]: forward, 
            fact[1]: backward,
        })
        
    return mat

def convert(mat: Mapping[str, Mapping[str, float]], query: Tuple[float, str, str], visited: Union[Set[str], None] = None) -> Union[float, None]:
    value, unit_from, unit_to = query
    visited = set((unit_from,)) if visited is None else visited
    
    #print("query: ", query)
    #print("visited: ", visited)
    
    options_to = mat.get(unit_from, None)
    if options_to is None:
        return None
    
    for option_to in options_to.keys():
        if option_to in visited:
            continue
        
        converted_value = value * options_to[option_to]
        if option_to == unit_to:
            return round(converted_value, 2)
        
        result = convert(mat, (converted_value, option_to, unit_to), visited.union((option_to,)))
        if result is not None:
            return result
        
    return None

mat = make_conversion_matrix(*parse_facts(*input_facts))
print(mat)

for query in parse_queries(*input_queries):
    print(query[0], query[1], "->", query[2])
    print(convert(mat, query))