Given a string txt and a string pat, your task is to find all occurrences of pat and its k-tuples in txt, but with the following constraints:
Input:
txt = "BACDGABCDA"
pat = "ABCD"
L = 4
Output:
[0, 5, 6]
Explanation: The valid substrings that are k-tuples of pat and within the length constraint are "BACD" at index 0, "ABCD" at index 5, and "BCDA" at index 6.
Input:
txt = "AABBCDAAB"
pat = "AB"
L = 4
Explanation:
The function checks for all substrings of txt that can be formed using the characters in pat with repetition allowed, while also ensuring that the length of the substring does not exceed L.
The valid substrings of length up to L that can be formed from pat are:
"AB"
"BA"
The function finds the starting indices of these substrings in txt:
"AA" (indices 0 and 1) can form "AB" and "BA".
"AB" at index 5.
Thus, the output is [0, 1, 5], indicating the starting indices of the valid substrings.
This example demonstrates how to find occurrences of k-tuples (or bags) that are permutations with repetition, allowing for a more flexible approach to substring matching.
Flexible; default I/O policies apply.