(LeetCode) First Unique Character in a String - LeetCode

Description:

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.

Accepted

310,115

Submissions

613,252

Solution:

Attempt 1: Failed : Timeout Exception:

 

class Solution {
    public int firstUniqChar(String s) {
        if(s==null||s.length()==0){
        
            return -1;
        }
        
        for(int i = 0; i<s.length(); i++){
            
            if(Count(s, s.charAt(i))==1){
                
                return i ;
            }
        }
        return -1;
    }
    
    
    static int Count(String s, char a){
        
        int count = 0; 
        
        for(int i = 0; i < s.length(); i++){
            
            if(s.charAt(i) == a){
                count++;
            }
        }
        
        return count; 
    }
}

 

Second Attempt: Accepted

class Solution {
    public int firstUniqChar(String s) {
        if(s==null||s.length()==0){
        
            return -1;
        }
        
        int[] map = new int[26];
        
        //
        
        for(int i = 0; i<s.length(); i++){
            
            int a = map[(int)s.charAt(i)-97];
            
            a++;
            
            map[(int)s.charAt(i)-97] = a;
                
        }
        
        for(int i = 0; i<s.length(); i++){
           if(map[(int)s.charAt(i)-97]==1){
               return i;
           }
        }
        return -1;
    }
        
}