LeetCode-First Unique Character in a 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.

 

 

 

class Solution {
    public int firstUniqChar(String s) {
        Map<Character, Integer> map = new HashMap<Character, Integer>();
        for(int i=0; i<s.length(); i++){
            char c = s.charAt(i);
            if(!map.containsKey(c)){
                map.put(c,i);
            }
            else{
                map.put(c,-1);
            }  
        }
        int max= Integer.MAX_VALUE;
        for (Character key : map.keySet()){
               int i = map.get(key);
                if(i >=0 && i <= max){
                    max = i;
                }   
        }
        if(max == Integer.MAX_VALUE){
            return -1;
        }
        else{
            return max;
        }
    }
}

　　二刷：

class Solution {
    public int firstUniqChar(String s) {
        if(s == null || s.length() == 0){
            return -1;
        }
        Map<Character, Integer> map = new LinkedHashMap<>();
        for(int i= 0; i< s.length(); i++){
            char c = s.charAt(i);
            if(map.containsKey(c)){
                map.put(c, -1);
            }
            else{
                map.put(c,i);
            }
        }
        for(char c : map.keySet()){
            if(map.get(c) != -1){
                return map.get(c);
            }
        }
        return -1;
    }
}