Integer Replacement — LeetCode 397 Python Solution

The problem

Given a positive integer n, you can apply one of the following operations: If n is even, replace n with n / 2. If n is odd, replace n with either n + 1 or n - 1.

Example

Input

n = 8

Output

3

Explanation

8 -> 4 -> 2 -> 1

Python solution

class Solution:
    def integerReplacement(self, n: int) -> int:
        ans = 0
        while n != 1:
            if (n & 1) == 0:
                n >>= 1
            elif n != 3 and (n & 3) == 3:
                n += 1
            else:
                n -= 1
            ans += 1
        return ans

Complexity

Pattern: Bit Manipulation

Use XOR, masks and the low-bit trick to replace whole data structures with an integer. LeetCode 397. Integer Replacement is filed here because LeetCode tags it Bit Manipulation, which is the vocabulary this hub collects.

The bit manipulation guide has the Python template for the pattern and the 194 LeetCode problems that use it.

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