Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.
Examples:
s = "leetcode" return 0. s = "loveleetcode", return 2.
Note: You may assume the string contain only lowercase letters.
2 passes
class Solution { public int firstUniqChar(String s) { Map<Character, Integer> map = new HashMap<>(); for (int i = 0; i < s.length(); i++) { map.put(s.charAt(i), map.getOrDefault(s.charAt(i), 0) + 1); } for (int i = 0; i < s.length(); i++) { if (map.get(s.charAt(i)) == 1) return i; } return -1; } }
Just for grins, 1 pass的方法可以考虑用set +LinkedHashMap, LinkedHashMap default的特性是保证key insertion order, Java doc
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