1342. Number of Steps to Reduce a Number to Zero (Easy)

Q

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

A:

if( (num & 1) ==0)

和 if (num &1 ==0)

结果是不一样的。操，我是个SB

--------直接计算---------------------

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

*****************计算1 的数量，和最高的 1 的位数*****************