Introduction

In this blog post, we will explore how to solve the LeetCode problem "1342" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

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

Explanation

Here's the solution to the problem:

• Bit Manipulation: The most efficient approach leverages bit manipulation. Dividing by 2 is equivalent to a right bit shift (>> 1). Checking if a number is even or odd is equivalent to checking the least significant bit (LSB) using a bitwise AND with 1 (& 1).

• Counting Operations: We can iterate through the bits of the number, incrementing the step count. If the LSB is 0 (even), we right shift. If the LSB is 1 (odd), we subtract 1 (which effectively flips the LSB to 0) and right shift. A special condition needs to be handled for the number 1 to avoid an extra increment at the end.

• Runtime Complexity: O(log n), where n is the input number. Storage Complexity: O(1).

Code

    def numberOfSteps(num: int) -> int:
    steps = 0
    while num > 0:
        if num % 2 == 0:
            num //= 2
        else:
            num -= 1
        steps += 1
    return steps