Number rotation-CodePudding

A rotation of a number n is constructed by shifting digits from one end of the number to the other. For example, 1234 rotated once to the right is 4123. If you continue rotating this number to the right, you get 3412, 2341, and finally 1234 again.

Note that zeros are preserved when rotating. So 250 rotated once is 25, and rotated twice is 502.

With this in mind, write the function isRotation(x, y) which takes two non-negative integers x and y, and returns True if x is a rotation of y or y is a rotation of x, and False otherwise.

Here is my code so far:

def counter(n):
    count = 0
    while n > 0:
        count  = 1
        n //= 10
    return count

def isRotation(x, y):
    if counter(x) == 0:
        if y == 0:
            return True
        return False
    if x == y:
        return True
        
    c = counter(x)
    
    for n in range(counter(x)):
        if counter(x) != c:
            rightest = x // 10 ** 0 % 10
            fm = (rightest * 10 ** (counter(x)))
            v2 = fm   (x//10)
            x = v2
            if v2 == y:
                return True
        if x < 100:
            rightest = x // 10 ** 0 % 10
            fm = (rightest * 10 ** (counter(x)))
            v1 = fm   (x//10)
            x = v1
            if v1 == y:
                return True
        rightest = x // 10 ** 0 % 10
        fm = (rightest * 10 ** (counter(x)-1))
        v = fm   (x//10)
        x = v
        if v == y:
            return True
    return False

# isRotation(6616, 66160) returns False instead of True

CodePudding user response：

There seems to be a lot of complexity in your solution, consider this:

import math


def is_rotation(x, y):
    t, f = x, 10 ** math.floor(math.log10(x)) if x else 0
    while True:
        if t == y:
            return True
        t = t // 10   t % 10 * f
        if t == x:
            return False


print(is_rotation(1234, 4123))
print(is_rotation(1234, 2341))
print(is_rotation(1234, 1234))

print(is_rotation(1234, 4321))
print(is_rotation(1234, 12345))
print(is_rotation(1234, 0))
print(is_rotation(0, 1234))

Result:

True
True
True
False
False
False
False

CodePudding user response：

You did not explicitly ask a question, but because I'm not a bot, I can make a reasonable inference from your comment at the end of your code (# isRotation(6616, 66160) returns False instead of True that you are implicitly asking what the problem is with your code.

StackOverflow article "How do I write a good answer?" prescribes to "Make sure your answer provides that – or at least a viable alternative." I don't know what the problem is with your code; therefore, I provide a viable alternative below:

def Rotations(a):
    a_str = str(a)
    L = len(a_str)

    my_list = [a]
    for i in range(L):
        a_str = a_str[-1]   a_str[0:-1]
        my_list.append(int(a_str))
    return my_list

def isRotation(x, y):
    return (x in Rotations(y)) or (y in Rotations(x))