LC-2351 Easy LeetCode

2351. First Letter to Appear Twice

Hash Table String Bit Manipulation Counting

Read the full problem statement on LeetCode.

Difficulty: easy Acceptance: 74% Topics: Hash Table, String, Bit Manipulation, Counting

Reading material

Arrays & Hashing 12 min Strings 12 min Bit Manipulation 10 min

Reference solution (spoiler · python)

# Time:  O(n)
# Space: O(1)

# hash table
class Solution(object):
    def repeatedCharacter(self, s):
        """
        :type s: str
        :rtype: str
        """
        lookup = set()
        for c in s:
            if c in lookup:
                break
            lookup.add(c)
        return c

Solution from kamyu104/LeetCode-Solutions · MIT