Same Letter at Both Ends

Medium

You are given a string text and a letter letter. Count the non-empty substrings of text that both start and end with letter. Substrings at different positions count separately, even if they read the same. A one-character substring equal to letter counts too.

Example 1

text='banana', letter='a' → 6

There are three a's. The three single "a"s qualify, plus "ana", "anana" and a second "ana": 6 in total.

Example 2

text='kiwi', letter='p' → 0

There is no "p" in the string, so there are no such substrings.

Example 3

text='ooo', letter='o' → 6

Constraints

1 ≤ len(text) ≤ 10⁵
text consists of lowercase English letters
letter is a single lowercase English letter

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Topics

Math String Counting

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Input

text='banana', letter='a'

Expected

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