387. 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.

分析：找出字符串中第一次出现且不重复的字符，返回其字符的下标，如果不存在就返回-1.

     用hashMap进行求，hashMap中可以通过ey-value的存储位置对和位置，对数据进行标记

 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,-1);
            }else{
                map.put(c,1);
            }
        }
        
        for(int i=0;i<s.length();i++){
            if(map.get(s.charAt(i))==1){
                return i;
            }
        }
        return -1;
    }