LeetCode

1342. Number of Steps to Reduce a Number to Zero

文章目录
  1. 1. 题目
  2. 2. 思路

题目

常用的图床正在维护所以这次就复制题目了。

Given an integer num, return the number of steps to reduce it to zero.

In one step, if the current number is even, you have to divide it by 2, otherwise, you have to subtract 1 from it.

Example 1:

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Input: num = 14
Output: 6
Explanation: 
Step 1) 14 is even; divide by 2 and obtain 7. 
Step 2) 7 is odd; subtract 1 and obtain 6.
Step 3) 6 is even; divide by 2 and obtain 3. 
Step 4) 3 is odd; subtract 1 and obtain 2. 
Step 5) 2 is even; divide by 2 and obtain 1. 
Step 6) 1 is odd; subtract 1 and obtain 0.

Example 2:

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Input: num = 8
Output: 4
Explanation: 
Step 1) 8 is even; divide by 2 and obtain 4. 
Step 2) 4 is even; divide by 2 and obtain 2. 
Step 3) 2 is even; divide by 2 and obtain 1. 
Step 4) 1 is odd; subtract 1 and obtain 0.

Example 3:

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Input: num = 123
Output: 12

思路

这道题最简单的方法无非是明面上的那种，循环遍历完事：

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class Solution(object):
    def numberOfSteps(self, num):
        """
        :type num: int
        :rtype: int
        """
        count=0
        while(num!=0):
            if (num %2) ==0:
                num=num/2
                count+=1
            else:
                num=num-1
                count+=1
        return count

但是我猜应该还存在位运算的方式，最近我在看CSAPP的相关课程，感觉可以尝试下运用学到的东西用位运算的方式重新做一下这道题。

（啥时候做完啥时候删这条）