Introduction

In this blog post, we will explore how to solve the LeetCode problem "1316" 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

Return the number of distinct non-empty substrings of text that can be written as the concatenation of some string with itself (i.e. it can be written as a + a where a is some string). Example 1: Input: text = "abcabcabc" Output: 3 Explanation: The 3 substrings are "abcabc", "bcabca" and "cabcab". Example 2: Input: text = "leetcodeleetcode" Output: 2 Explanation: The 2 substrings are "ee" and "leetcodeleetcode". Constraints: 1 <= text.length <= 2000 text has only lowercase English letters.

Explanation

Here's the approach, complexity analysis, and Python code for solving this problem:

• Iterate and Check: Iterate through all possible substring lengths and starting positions within the input string text. For each substring, check if its length is even and if the first half is equal to the second half.
• Store Unique Substrings: Use a set to store the distinct repeating substrings found to avoid counting duplicates.

• Return Count: Finally, return the size of the set, which represents the number of distinct repeating substrings.

• Runtime Complexity: O(n^3), where n is the length of the input string.

• Storage Complexity: O(n), where n is the length of the input string (in the worst case, the set could store n/2 repeating substrings).

Code

    def distinct_echo_substrings(text: str) -> int:
    """
    Finds the number of distinct non-empty substrings of text that can be written as the concatenation of some string with itself (i.e. it can be written as a + a where a is some string).

    Example 1:
    Input: text = "abcabcabc"
    Output: 3
    Explanation: The 3 substrings are "abcabc", "bcabca" and "cabcab".

    Example 2:
    Input: text = "leetcodeleetcode"
    Output: 2
    Explanation: The 2 substrings are "ee" and "leetcodeleetcode".

    Args:
        text (str): The input string.

    Returns:
        int: The number of distinct repeating substrings.
    """

    distinct_substrings = set()
    n = len(text)

    for length in range(2, n + 1, 2):  # Iterate through even lengths only
        for i in range(n - length + 1):
            substring = text[i:i + length]
            half_length = length // 2
            first_half = substring[:half_length]
            second_half = substring[half_length:]

            if first_half == second_half:
                distinct_substrings.add(substring)

    return len(distinct_substrings)