Distinct Echo Substrings - Solution & Explanation

This approach involves utilizing a sliding window to iterate over possible substrings and employing hashing to detect if a substring is a repeated concatenation of a smaller substring. The advantage of hashing is that it allows comparison of substrings in O(1) time, making the solution efficient.

This Python function calculates the number of distinct echo substrings by iterating over possible substring lengths up to half of the text length. It uses a sliding window to compare each substring of length 'length' with the succeeding substring of the same length. If they are equal, it stores the combined substring in a set to ensure uniqueness.

This approach uses Dynamic Programming (DP) to keep track of repeated substring patterns. A DP table can help store results of previous computations, thus optimizing the check for repeated substrings by re-using calculated solutions.

The Python implementation uses a 2D DP table where dp[i][j] stores the length of the longest common suffix of text[i:] and text[j:]. It stores unique echo substrings in a set. The function performs checks to ensure that only valid echo substrings are stored.