花花酱 LeetCode 1784. Check if Binary String Has at Most One Segment of Ones

Given a binary string s ​​​​​without leading zeros, return true​​​ if s contains at most one contiguous segment of ones. Otherwise, return false.

Example 1:

Input: s = "1001"
Output: false
Explanation: The ones do not form a contiguous segment.

Example 2:

Input: s = "110"
Output: true

Constraints:

• 1 <= s.length <= 100
• s[i]​​​​ is either '0' or '1'.
• s[0] is '1'.

Solution: Counting

increase counter if s[i] == ‘1’ otherwise, reset counter.
increase counts when counter becomes 1.
return counts == 1

Time complexity: O(n)
Space complexity: O(1)