Day 18: 387. First Unique Character in a String

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asd32499522 2025-10-16 16:29:59 ‧ 118 瀏覽

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Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1.

Example 1:
Input: s = "leetcode"
Output: 0
Explanation:
The character 'l' at index 0 is the first character that does not occur at any other index.
Example 2:
Input: s = "loveleetcode"
Output: 2
Example 3:
Input: s = "aabb"
Output: -1
解題思路
1.先統計每個字母出現的次數（用int[26]）。
2.再遍歷一次字串，找出第一個只出現一次的字母。