Leetcode 2124: Check if All A's Appears Before All B's

Input: You are given a string s consisting of only the characters 'a' and 'b'.

Example: s = 'aaaabbb'

Constraints:

• 1 <= s.length <= 100

• s[i] is either 'a' or 'b'.

Output: Return true if every 'a' appears before every 'b' in the string. Otherwise, return false.

Example: Input: 'aaabbb' -> Output: true

Constraints:

• The input string will contain only 'a' and 'b'.

Goal: Determine if all 'a' characters in the string appear before all 'b' characters.

Steps:

• Check if the substring 'ba' exists in the string.

• If 'ba' is found, return false. Otherwise, return true.

Goal: The string will have a length between 1 and 100, and each character will be either 'a' or 'b'.

Steps:

• The string length is between 1 and 100.

• The string contains only the characters 'a' and 'b'.

Assumptions:

• The string contains only 'a' and 'b'.

• There will be at least one character in the string.

• Input: Input: 'aaaabbb'

• Explanation: In this case, all the 'a's appear before the 'b's, so we return true.

• Input: Input: 'abab'

• Explanation: Here, an 'a' appears after a 'b', so we return false.

Approach: To solve this problem, check if the substring 'ba' exists in the input string. If it does, it means there is a 'b' before an 'a', which violates the condition.

Observations:

• We only need to check if the substring 'ba' is present in the string.

• If 'ba' is found in the string, return false. Otherwise, return true.

Steps:

• Search for the substring 'ba' in the string.

• If 'ba' is found, return false.

• If 'ba' is not found, return true.

Empty Inputs:

• An empty string is not a valid input according to the problem constraints.

Large Inputs:

• Ensure that the solution works for strings with up to 100 characters.

Special Values:

• Strings that consist only of 'a's or 'b's will automatically return true.

Constraints:

• The solution should handle the maximum string length efficiently.

bool checkString(string s) {
    return s.find("ba")==string::npos;
}

1 : Function Definition

bool checkString(string s) {

This line defines a function named checkString, which takes a string 's' as input and returns a boolean value.

2 : String Search

    return s.find("ba")==string::npos;

This line searches for the substring 'ba' in the input string 's'. If 'ba' is not found, the function returns true; otherwise, it returns false.

Best Case: O(n)

Average Case: O(n)

Worst Case: O(n)

Description: We check if 'ba' exists in the string, which takes O(n) time, where n is the length of the string.

Best Case: O(1)

Worst Case: O(1)

Description: The solution uses a constant amount of extra space.

Leetcode 2124: Check if All A's Appears Before All B's

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