Integer Replacement

Given a positive integer n, you can apply one of the following operations:

1. If n is even, replace n with n / 2.
2. If n is odd, replace n with either n + 1 or n - 1.

Return the minimum number of operations needed for n to become 1.

Example 1:

Input: n = 8
Output: 3
Explanation: 8 -> 4 -> 2 -> 1

Example 2:

Input: n = 7
Output: 4
Explanation: 7 -> 8 -> 4 -> 2 -> 1
or 7 -> 6 -> 3 -> 2 -> 1

Example 3:

Input: n = 4
Output: 2

Constraints:

• 1 <= n <= 231 - 1

SOLUTION:

class Solution:
    def integerReplacement(self, n: int) -> int:
        if n == 1:
            return 0
        if n == 3:
            return 2
        if n & 1:
            if (n + 1) & 3 == 0:
                return 3 + self.integerReplacement((n + 1) >> 2)
            else:
                return 2 + self.integerReplacement((n - 1) >> 1)
        else:
            return 1 + self.integerReplacement(n >> 1)