[LeetCode] #387 字符串中的第一个唯一字符

class Solution {
    public int firstUniqChar(String s) {
        for(int i = 0; i < s.length(); i++){
            String temp = s.substring(0,i) + s.substring(i+1);
            int res = temp.indexOf(s.charAt(i));
            if(res == -1) return i;
        }
        return -1;
    }
}

class Solution {
    public int firstUniqChar(String s) {
        for (int i = 0; i < s.length(); i++) 
            if (s.indexOf(s.charAt(i)) == s.lastIndexOf(s.charAt(i))) return i;
        return -1;
    }
}

class Solution {
    public int firstUniqChar(String s) {
        Map<Character, Integer> frequency = new HashMap<Character, Integer>();
        for (int i = 0; i < s.length(); ++i) {
            char ch = s.charAt(i);
            frequency.put(ch, frequency.getOrDefault(ch, 0) + 1);
        }
        for (int i = 0; i < s.length(); ++i) {
            if (frequency.get(s.charAt(i)) == 1) {
                return i;
            }
        }
        return -1;
    }
}

class Solution {
    public int firstUniqChar(String s) {
        int[] arr = new int[26];
        int n = s.length();
        for (int i = 0; i < n; i++) arr[s.charAt(i)-‘a‘]++ ;
        for (int i = 0; i < n; i++) 
            if (arr[s.charAt(i)-‘a‘] == 1) return i;
        return -1;
    }
}