LeetCode contest 183 5377. 将二进制表示减到 1 的步骤数
Table of Contents
一、中文版
给你一个以二进制形式表示的数字 s 。请你返回按下述规则将其减少到 1 所需要的步骤数：
如果当前数字为偶数，则将其除以 2 。
如果当前数字为奇数，则将其加上 1 。
题目保证你总是可以按上述规则将测试用例变为 1 。
示例 1：
输入：s = "1101"
输出：6
解释："1101" 表示十进制数 13 。
Step 1) 13 是奇数，加 1 得到 14
Step 2) 14 是偶数，除 2 得到 7
Step 3) 7 是奇数，加 1 得到 8
Step 4) 8 是偶数，除 2 得到 4
Step 5) 4 是偶数，除 2 得到 2
Step 6) 2 是偶数，除 2 得到 1
示例 2：
输入：s = "10"
输出：1
解释："10" 表示十进制数 2 。
Step 1) 2 是偶数，除 2 得到 1
示例 3：
输入：s = "1"
输出：0
提示：
1 <= s.length <= 500
s 由字符 '0' 或 '1' 组成。
s[0] == '1'
二、英文版
Given a number s in their binary representation. Return the number of steps to reduce it to 1 under the following rules: If the current number is even, you have to divide it by 2. If the current number is odd, you have to add 1 to it. It's guaranteed that you can always reach to one for all testcases. Example 1: Input: s = "1101" Output: 6 Explanation: "1101" corressponds to number 13 in their decimal representation. Step 1) 13 is odd, add 1 and obtain 14. Step 2) 14 is even, divide by 2 and obtain 7. Step 3) 7 is odd, add 1 and obtain 8. Step 4) 8 is even, divide by 2 and obtain 4. Step 5) 4 is even, divide by 2 and obtain 2. Step 6) 2 is even, divide by 2 and obtain 1. Example 2: Input: s = "10" Output: 1 Explanation: "10" corressponds to number 2 in their decimal representation. Step 1) 2 is even, divide by 2 and obtain 1. Example 3: Input: s = "1" Output: 0 Constraints: 1 <= s.length <= 500 s consists of characters '0' or '1' s[0] == '1'
三、My answer
class Solution: def numSteps(self, s: str) -> int: s_int = int(s,2) ans = 0 while s_int != 1: if s_int % 2 == 1: s_int += 1 else: s_int //= 2 ans += 1 return ans
四、解题报告
按照题意模拟即可。
注意：
s_int //= 2，不要写成 s_int /= 2，在例子 "1111011110000011100000110001011011110010111001010111110001" 报错。
可见虽然偶数时除以2，也明知道会整除，还是需要用 // 整除符号。
