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LeetCode Question 1342: Number of Steps to Reduce a Number to Zero - My Simple Solution

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SeriesLeetCodepart 4 of 10
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  3. Leetcode Question 412: Fizz Buzz - My Simple Solution
  4. LeetCode Question 1342: Number of Steps to Reduce a Number to Zero - My Simple Solution
  5. Solving LeetCode Problem 876: Middle of the Linked List
  6. LeetCode Question 383: Ransom Note Solution Breakdown
  7. LeetCode 977: Squares of a Sorted Array Solution
  8. LeetCode 1295: Find Numbers with Even Number of Digits
  9. LeetCode 485 - Finding Max Consecutive Ones
  10. Is Bitwise & Better than Arithmetic to Determine Even or Odd? Let’s Dive In!
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Let’s kick things off with the problem statement. The challenge is to find out how many steps it takes to reduce a number to zero, where the steps are defined as follows:

  • If the number is even, divide it by 2.
  • If it’s odd, subtract 1 from it.

Sounds straightforward, right? Like, how hard can it be to reduce an integer to zero with just those two operations? Well, let’s throw some Java code into the mix to show you how it’s done!

My Java Solution

Here’s the code I came up with:

class Solution {
    public int numberOfSteps(int num) {
        int i = 0; // This will count our steps
        while (num > 0) {
            i++; // Increment step count
            if (num % 2 == 0) {
                num = num / 2; // Even, so divide
            } else {
                num = num - 1; // Odd, so subtract
            }
        }
        return i; // Return total steps taken
    }
}

A Quick Example

Let’s see this in action with an example.

Say the input is num = 14. Here’s how the steps would play out:

  • Start with 14 (even) → divide by 2 → 7
  • 7 (odd) → subtract 1 → 6
  • 6 (even) → divide by 2 → 3
  • 3 (odd) → subtract 1 → 2
  • 2 (even) → divide by 2 → 1
  • 1 (odd) → subtract 1 → 0

So, the total steps would be 6.

Performance and Complexity

In terms of performance:

  • Time Complexity: O(log n) — This is because every time you divide by 2, you effectively halve the number of operations needed.
  • Space Complexity: O(1) — We’re only using a fixed amount of space (the variable i).

References

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