Greatest English Letter in Upper and Lower Case — LeetCode 2309 Python Solution

The problem

Given a string of English letters s, return the greatest English letter which occurs as both a lowercase and uppercase letter in s. The returned letter should be in uppercase.

Example

Input

s = "lEeTcOdE"

Output

"E"

Explanation

The letter 'E' is the only letter to appear in both lower and upper case.

Python solution

class Solution:
    def greatestLetter(self, s: str) -> str:
        ss = set(s)
        for c in ascii_uppercase[::-1]:
            if c in ss and c.lower() in ss:
                return c
        return ''

Complexity

Pattern: Hash Map

Trade memory for time: remember what you have seen so the second pass never happens. LeetCode 2309. Greatest English Letter in Upper and Lower Case is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Hash Table.

The hash map guide has the Python template for the pattern and the 709 LeetCode problems that use it.

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