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All topics›JavaScript›Hashing

First Unique Character in a String

beginnerlayer B3 · Hashing5 tests

Given a string s, return the index of the first character that appears exactly once. If every character repeats, return -1.

  • s contains lowercase letters only
  • 'leetcode' gives 0; 'loveleetcode' gives 2
  • An empty string returns -1

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