387. First Unique Character

/* Given a string, find the first non-repeating character in it and return its index. If it doesn't exist, return -1.

Examples:

s = "leetcode"
return 0.

s = "loveleetcode"
return 2.
 

Note: You may assume the string contains only lowercase English letters.
Question link: https://leetcode.com/problems/first-unique-character-in-a-string/

*/

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Code: 

class Solution {
    public int firstUniqChar(String s) {
        
        if(s.length() == 0){
            return -1;
        }
        HashMap<Character, Integer> map = new HashMap<Character,Integer>();   
        int ans = -1;
        
        for(int i = 0; i<s.length(); i++){
            if(map.containsKey(s.charAt(i))){
                
                map.put(s.charAt(i), map.get(s.charAt(i)) + 1);
            }else{
                map.put(s.charAt(i), 1);
            }
        }
        
       for(int i = 0; i<s.length(); i++){
          if(map.get(s.charAt(i)) == 1){
              ans = i;
              break;
          }
       }
        return ans;
        
    }
}