[LeetCode]Integer Replacement

题目描述：

LeetCode 397. Integer Replacement

Given a positive integer n and you can do operations as follow:

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

What is the minimum number of replacements needed for n to become 1?

Example 1:

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

Example 2:

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

题目大意：

给定正整数n，你可以做如下操作：

如果n是偶数，将n替换为n/2

如果n是奇数，你可以将n替换为n + 1或者n - 1

求将n替换为1的最小次数

解题思路：

由于递归深度较小，因此直接根据题意递归求解即可

Python代码：

class Solution(object):
    def integerReplacement(self, n):
        """
        :type n: int
        :rtype: int
        """
        if n == 1: return 0
        if n & 1 == 0: return self.integerReplacement(n / 2) + 1
        return min(self.integerReplacement(n + 1), self.integerReplacement(n - 1)) + 1