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'
class Solution:
    def numSteps(self, s: str) -> int:
        i, mid_zero = 0 , 0 
        for j in range(1, len(s)):
            if s[j] == '1':
                mid_zero += j -i - 1
                i = j
        if i == 0:
            return len(s)-1
        return mid_zero + 1 + len(s)

class Solution:
    def numSteps(self, s: str) -> int:
        i, mid_zero = 0 , 0 
        for j in range(1, len(s)):
            if s[j] == '1':
                mid_zero += j -i - 1
                i = j
        if i == 0:
            return len(s)-1
        return mid_zero + 1 + len(s)
