Question

I have certain algorithm need to implement. Basically the rules are:

1. The first whitespace-separated token on a line will be the word being defined.
2. The later tokens will be the definition. If the definition is “.”, that word is a primitive, i.e., a word with no definition.
3. The output is a single comma-separated line of text containing each word in the dictionary exactly once. Each word is only to be printed after all of the words in its definition. Note that for certain input sets, there may be multiple valid outputs.

For example the input:

Civic        Honda Car
Honda        Manufacturer
VW           Manufacturer
Manufacturer .
Car          .
Beetle       VW Car

Some Possible Outputs:

Car, Manufactor, Honda, VW, Beetle, Civic
Manufacturer, VW, Car, Beetle, Honda, Civic
Manufacturer, Honda, VW, Car, Beetle, Civic

My implementation:

def defIt(pre, cur):
    # If previous and current strings are the same, no action take
    if pre == cur:
        return pre

    # Split two strings to list
    l_pre = pre.split()
    l_cur = cur.split()

    # If previous string length is shorter than the current string     length, then swap two lists
    if len(l_pre) < len(l_cur):
        l_pre, l_cur = l_cur, l_pre

    found = False


    for j, w_cur in enumerate(l_cur):
        for i, w_pre in enumerate(l_pre):
            if w_pre == w_cur:
                found = True
                return ' '.join(l_cur[j:] + l_cur[:j] + l_pre[:i] + l_pre[(i + 1):])


    if not found:
        return ' '.join(l_cur[1:] + [l_cur[0]] + l_pre)

Just cannot get it right. What do I missing? Thanks a lot.

Answer 1

def read_graph(lines):
    g = {}
    for line in lines:
        words = line.split()
        if words[1] == '.':
            words = words[:1]
        g[words[0]] = words[1:]
    return g

def dump_graph(g):
    out = []
    def dump(key):
        for k in g[key]:
            dump(k)
        if key not in out:
            out.append(key)
    for k in g:
        dump(k)
    return out

Usage:

>>> data = """Civic        Honda Car
... Honda        Manufacturer
... VW           Manufacturer
... Manufacturer .
... Car          .
... Beetle       VW Car
... """
>>> g = read_graph(data.splitlines())
>>> g
{'VW': ['Manufacturer'], 'Civic': ['Honda', 'Car'], 'Car': [],
'Honda': ['Manufacturer'], 'Beetle': ['VW', 'Car'], 'Manufacturer': []}
>>> dump_graph(g)
['Manufacturer', 'VW', 'Honda', 'Car', 'Civic', 'Beetle']
>>>

Every word in the resulting list comes after all its “definition” words.