First Unique Character In A String

First Unique Character In A String string

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.

First Unique Character In A String Solution

class FirstUniqueCharacterInAString {
    public int firstUniqChar(String s) {
        HashMap<Character, Integer> characters = new HashMap<Character, Integer>();
        for(int i = 0; i < s.length(); i++) {
            char current = s.charAt(i);
            if(characters.containsKey(current)) {
                characters.put(current, -1);
            } else {
                characters.put(current, i);
            }
        }

        int min = Integer.MAX_VALUE;
        for(char c: characters.keySet()) {
            if(characters.get(c) > -1 && characters.get(c) < min) {
                min = characters.get(c);
            }
        }

        return min == Integer.MAX_VALUE ? -1 : min;

    }
}

Last modified October 4, 2020