12. Number of Steps to Reduce a Number to Zero.cpp

/*
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

Hint #1  
Simulate the process to get the final answer.
*/

class Solution
{
public:
  int numberOfSteps(int num)
  {
    if (num == 0)
      return 0;
    int ans = 0;
    if (num % 2 == 0)
      ans += numberOfSteps(num / 2);
    else
      ans += numberOfSteps(num - 1);
    return ans + 1;
  }
};