#1784

Check if Binary String Has at Most One Segment of Ones

Easy
StringTwo PointersSliding Window
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Approaches

Brute ForceOptimal
Complexity Comparison
Brute ForceOptimal Solution
Time
O(n²)
O(n)
Space
O(1)
O(1)
💡

Intuition

Time O(n)Space O(1)

The optimal solution involves a single pass through the string to count the segments of '1's. This is efficient because we only need to check transitions from '0' to '1'.

⚙️

Algorithm

5 steps
  1. 1Step 1: Initialize a counter for segments of '1's.
  2. 2Step 2: Traverse the string character by character.
  3. 3Step 3: Increment the counter when a '1' is found that follows a '0' or is the first character.
  4. 4Step 4: If the counter exceeds 1 at any point, return false.
  5. 5Step 5: If the loop completes and the counter is 1 or less, return true.
solution.py8 lines
1def checkOnesSegment(s):
2    count = 0
3    for i in range(len(s)):
4        if s[i] == '1' and (i == 0 or s[i-1] == '0'):
5            count += 1
6        if count > 1:
7            return False
8    return True

Complexity note: The complexity is O(n) because we only make a single pass through the string, checking each character once.

  • 1A segment of '1's is defined by transitions from '0' to '1'.
  • 2The problem can be solved efficiently by counting these transitions.

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