Introduction

In this blog post, we will explore how to solve the LeetCode problem "2696" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

You are given a string s consisting only of uppercase English letters. You can apply some operations to this string where, in one operation, you can remove any occurrence of one of the substrings "AB" or "CD" from s. Return the minimum possible length of the resulting string that you can obtain. Note that the string concatenates after removing the substring and could produce new "AB" or "CD" substrings. Example 1: Input: s = "ABFCACDB" Output: 2 Explanation: We can do the following operations: - Remove the substring "ABFCACDB", so s = "FCACDB". - Remove the substring "FCACDB", so s = "FCAB". - Remove the substring "FCAB", so s = "FC". So the resulting length of the string is 2. It can be shown that it is the minimum length that we can obtain. Example 2: Input: s = "ACBBD" Output: 5 Explanation: We cannot do any operations on the string so the length remains the same. Constraints: 1 <= s.length <= 100 s consists only of uppercase English letters.

Explanation

Here's the solution to the problem, explained and implemented in Python:

• Approach:

  • Use a stack to simulate the string reduction process.
  • Iterate through the input string, and for each character, push it onto the stack.
  • If the top two elements of the stack form "AB" or "CD", pop them from the stack.

• Complexity:

  • Runtime: O(n), where n is the length of the input string. Storage: O(n) in the worst case where no reductions are possible and the stack stores the entire string.

Code

    def min_length(s: str) -> int:
    """
    Given a string s consisting only of uppercase English letters. You can apply some operations to this string where,
    in one operation, you can remove any occurrence of one of the substrings "AB" or "CD" from s.
    Return the minimum possible length of the resulting string that you can obtain.
    Note that the string concatenates after removing the substring and could produce new "AB" or "CD" substrings.

    For example:
    min_length("ABFCACDB") == 2
    min_length("ACBBD") == 5
    """
    stack = []
    for char in s:
        stack.append(char)
        while len(stack) >= 2:
            top = stack[-1]
            second_top = stack[-2]
            if (second_top == 'A' and top == 'B') or (second_top == 'C' and top == 'D'):
                stack.pop()
                stack.pop()
            else:
                break
    return len(stack)