LeetCode 1342. Number of Steps to Reduce a Number to Zero

Description

https://leetcode.com/problems/number-of-steps-to-reduce-a-number-to-zero/

Given a non-negative integer num, return the number of steps to reduce it to zero. If the current number is even, you have to divide it by 2, otherwise, you have to subtract 1 from it.

Example 1:

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:

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:

Input: num = 123
Output: 12

Constraints:

  • 0 <= num <= 10^6

Explanation

Just by implementing the step instructions and it would work.

Python Solution

class Solution:
    def numberOfSteps (self, num: int) -> int:
        steps = 0
        
        while num > 0:
            if num % 2 == 0:
                num = num // 2
            else:
                num -= 1
            steps += 1
        
        return steps
  • Time Complexity: O(N)
  • Space Complexity: O(1)

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