Gray rank algorithm implementation in python

Question

How can I implement the following algorithm in python:

def getGraycodeRank(n, t):
    r = 0#range
    b = 0
    for i in reversed(range(0, n)):
        if n - i IS IN t: #how to check it?
            b = 1-b
        if b == 1:
            r += 2^i
    return r

Christian Tapia · Answer 1 · 2014-04-05T08:09:26.970

0

You can use the in operator:

if (n - i) in t:

or simply

if n - i in t:

Also, the operator ^ doesn't do what you think. To get the power of a number, use **:

r += 2**i

Note:

The in operator will work with tuples, lists, dicts, strings.

Edit:

Since t is a string, to check if an integer (n - i) is contained by t, you will have to convert the integer n - i to a string:

if str(n - i) in `t`:
    # ...

edited Apr 05 '14 at 08:09

answered Apr 05 '14 at 07:50

Christian Tapia

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assuming `t` is a `dict` or `list`. – Srikar Appalaraju Apr 05 '14 at 07:51
when I tried to run: print getGraycodeRank(4, "101") I get: if (n - i) in t: #how to check it? TypeError: 'in ' requires string as left operand, not int – Michal_Szulc Apr 05 '14 at 07:59
@Fos What is the type of `n` and `t`? – Christian Tapia Apr 05 '14 at 08:00
@Fos you will have to convert the integer `4` to a *string*: `n = str(n)` – Christian Tapia Apr 05 '14 at 08:01
I dont get it. now I get error: for i in reversed(range(0, n)): TypeError: range() integer end argument expected, got str. – Michal_Szulc Apr 05 '14 at 08:05
@Fos sorry for that. Try the new edit. Only use `str()` in the `if` so you can use the operator `in`. You will need `n` to be an integer in the other operations. – Christian Tapia Apr 05 '14 at 08:10

score 0 · Answer 2 · answered Apr 05 '14 at 07:52

0

assuming t is a dict or list

if (n - i) in t:

this should work...

answered Apr 05 '14 at 07:52

Srikar Appalaraju

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Gray rank algorithm implementation in python

2 Answers2