Where the Fragment Starts

Easy

You get two strings, text and fragment. Find the index at which fragment first appears in text as a contiguous piece and return it (0-based). If fragment does not appear in text at all, return -1. Try not to lean on built-in substring search: the search itself is the point of the exercise.

Example 1

text='bananas', fragment='ana' → 1

"ana" appears at positions 1 and 3 (the occurrences overlap). The first one is 1.

Example 2

text='kettle', fragment='kettles' → -1

The fragment is longer than the text itself, so it cannot be found: the answer is −1.

Example 3

text='abcabd', fragment='abd' → 3

Constraints

1 ≤ len(text), len(fragment) ≤ 10⁵
Both strings consist of lowercase English letters

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Topics

Two Pointers String String Matching

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Input

text='bananas', fragment='ana'

Expected

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