Introduction

In this blog post, we will explore how to solve the LeetCode problem "521" 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

Given two strings a and b, return the length of the longest uncommon subsequence between a and b. If no such uncommon subsequence exists, return -1. An uncommon subsequence between two strings is a string that is a subsequence of exactly one of them. Example 1: Input: a = "aba", b = "cdc" Output: 3 Explanation: One longest uncommon subsequence is "aba" because "aba" is a subsequence of "aba" but not "cdc". Note that "cdc" is also a longest uncommon subsequence. Example 2: Input: a = "aaa", b = "bbb" Output: 3 Explanation: The longest uncommon subsequences are "aaa" and "bbb". Example 3: Input: a = "aaa", b = "aaa" Output: -1 Explanation: Every subsequence of string a is also a subsequence of string b. Similarly, every subsequence of string b is also a subsequence of string a. So the answer would be -1. Constraints: 1 <= a.length, b.length <= 100 a and b consist of lower-case English letters.

Explanation

Here's a solution to find the length of the longest uncommon subsequence, optimized for efficiency.

• High-level approach: The key insight is that if the strings a and b are different, then the longer string (or either string if they are of equal length) is an uncommon subsequence of itself. If the strings are identical, then no uncommon subsequence exists. If one string is a subsequence of the other but they are not equal, the longer string is still the result.
• Complexity: Time complexity is O(1). Space Complexity is O(1).

Code

    def longest_uncommon_subsequence(a: str, b: str) -> int:
    """
    Given two strings a and b, return the length of the longest uncommon subsequence between a and b.
    If no such uncommon subsequence exists, return -1.
    An uncommon subsequence between two strings is a string that is a subsequence of exactly one of them.

    For Example:
    longest_uncommon_subsequence("aba", "cdc") == 3
    longest_uncommon_subsequence("aaa", "bbb") == 3
    longest_uncommon_subsequence("aaa", "aaa") == -1
    """

    if a == b:
        return -1
    else:
        return max(len(a), len(b))