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1342. Number of Steps to Reduce a Number to Zero

Difficulty Topics

Description

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

number-of-steps-to-reduce-a-number-to-zero.py
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
number-of-steps-to-reduce-a-number-to-zero.cpp
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;

    }
};