1342. Number of Steps to Reduce a Number to Zero

Problem Link

Description

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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:

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 <= 106

Solution

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Python3

class Solution:
    def numberOfSteps(self, num: int) -> int:
        res = 0
        
        while num > 0:
            res += 1
            
            if num % 2 == 0:
                num //= 2
            else:
                num -= 1
        
        return res

C++

class Solution {
public:
    int numberOfSteps (int num) {
        if (!num) return 0;
        int res = 0;
        
        while (num){
            res += (num&1) ? 2 : 1;
            num >>= 1;
        }
        
        return res - 1;
        
    }
};