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;
     }