387. first unique character in a string

string

https://leetcode.com/problems/first-unique-character-in-a-string/

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 Example 2: Input: s = “loveleetcode” Output: 2 Example 3: Input: s = “aabb” Output: -1

Constraints:

1 <= s.length <= 105 	
s consists of only lowercase English letters
  • code
class Solution {
    public int firstUniqChar(String s) {
        Map<Character, Integer> counter = new LinkedHashMap<>();
        for (char c: s.toCharArray()){
            counter.put(c, counter.getOrDefault(c, 0) + 1);
        }
        
        for (char c: counter.keySet()){
            if (counter.get(c) == 1) return s.indexOf(c);
        }
        return -1;
    }
}
  • code
class Solution:
    def firstUniqChar(self, s: str) -> int:
        char_count = dict(collections.Counter(s))
        for i in range(len(s)):
            if char_count[s[i]] == 1:
                return i
        return -1
  • code
import string

class Solution:
    def firstUniqChar(self, s: str) -> int:
        ret = len(s)
        for c in string.ascii_lowercase:
            l, r = s.find(c), s.rfind(c)
            if l != -1 and l == r:
                ret = min(ret, l)
        return ret if ret != len(s) else -1