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

Number of Steps to Reduce a Number to Zero (E)

题目

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

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题意

将一个数进行若干次偶数/2、奇数-1的操作，直至其变为0，求需要的操作次数。

思路

直接照做即可。

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代码实现

Java

class Solution {
    public int numberOfSteps (int num) {
        int steps = 0;
        while (num > 0) {
            num = num % 2 == 0 ? num / 2 : num - 1;
            steps++;
        }
        return steps;
    }
}