LeetCode [387] First Unique Character in a String

 387. First Unique Character in a String

Easy

Given a string, find the first non-repeating character in it and return its index. If it doesn't exist, return -1.

Examples:

s = "leetcode"
return 0.

s = "loveleetcode"
return 2.

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class Solution { public int firstUniqChar(String s) { Map<Character, Integer> map = new LinkedHashMap<>(); Set<Character> set = new HashSet<>(); for (int i = 0; i < s.length(); i++) { if (set.contains(s.charAt(i))) { map.remove(s.charAt(i)); } else { map.put(s.charAt(i), i); set.add(s.charAt(i)); } } return map.size() == 0 ? -1 : map.entrySet().iterator().next().getValue(); } }