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.

 1 public class Solution {
 2     public int firstUniqChar(String s) {
 3         int[] count = new int[26];
 4         for (int i=0; i<s.length(); i++) {
 5             count[s.charAt(i) - ‘a‘]++;
 6         }
 7         for (int i=0; i<s.length(); i++) {
 8             if (count[s.charAt(i) - ‘a‘] == 1) 
 9                 return i;
10         }
11         return -1;
12     }
13 }