397. Integer Replacement

Dynamic Programming Greedy Bit Manipulation Memoization

Problem - Integer Replacement

Medium

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

Solutions

Python3

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

Submission Stats:

• Runtime: 0 ms (100.00%)
• Memory: 17.8 MB (74.42%)