Question
For a string s, consider each starting index i (including 0). Index i counts if the substring of s that begins at i shares at least one leading character with s itself — equivalently, the Z-value z[i] is positive (and z[0] is the whole string by convention). Return how many indices count. For example, in "aabaab" the qualifying indices are 0, 1, 3, 4, so the answer is 4. The string can be up to 10^5 characters; aim for linear time.
count_prefix_matches(s: str) → int["aabaab"]out4State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.
Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.