How do you solve Check if All A's Appears Before All B's on LeetCode?

Check if All A's Appears Before All B's (LeetCode #2124) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(1) space complexity. Key insight: The problem can be simplified by checking for the presence of 'ba'.

What is the brute force solution for Check if All A's Appears Before All B's?

The brute force approach for Check if All A's Appears Before All B's is Brute Force, with O(n²) time complexity and O(1) space complexity. The brute force approach checks each character in the string to see if any 'b' appears before an 'a'. If it finds such a case, it returns false; otherwise, it returns true. This is straightforward but inefficient. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Check if All A's Appears Before All B's?

Check if All A's Appears Before All B's uses the following concepts: String. The recommended patterns to study are: String Manipulation, Two Pointers.

What are the interview tips for Check if All A's Appears Before All B's?

Always think about edge cases and how they might affect your solution. Explain your thought process clearly to the interviewer. Consider both brute force and optimal solutions to show your understanding.

What are common mistakes when solving Check if All A's Appears Before All B's?

Not considering edge cases like strings with only 'a's or 'b's. Overcomplicating the problem by using unnecessary loops.

#2124

Check if All A's Appears Before All B's

Easy

StringString ManipulationTwo Pointers

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(1)

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Intuition

Time O(n)Space O(1)

The optimal solution leverages the idea that we can check for the presence of the substring 'ba'. If it exists, it means there is at least one 'a' after a 'b', which violates our condition. This is efficient and straightforward.

⚙️

Algorithm

3 steps

1Step 1: Check if the substring 'ba' exists in the string.
2Step 2: If 'ba' is found, return false.
3Step 3: If 'ba' is not found, return true.

solution.py4 lines

1# Full working Python code
2
3def checkOrder(s):
4    return 'ba' not in s

ℹ

Complexity note: The time complexity is O(n) because we scan the string once to check for the substring 'ba'. The space complexity is O(1) since we are not using any additional data structures.

1The problem can be simplified by checking for the presence of 'ba'.
2Understanding string operations can lead to more efficient solutions.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.