leetcode--Longest Substring Without Repeating Characters

Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. For "bbbbb" the longest substring is "b", with the length of 1.

Code 1: The algorithm is simple and the running time is O(n), where n is the length of the string

public class Solution {
    public int lengthOfLongestSubstring(String s) {
       int max = 0;
		int length = s.length();
		if(length > 0){
			Map<Character, Integer> distinguish = new HashMap<Character, Integer>();
			int startIndex = 0;
			for(int i = 0; i < length; ++i){
				if(distinguish.containsKey(s.charAt(i))) {
					int temp = distinguish.get(s.charAt(i));
				
					for(int j = startIndex; j < temp + 1; ++j)
						distinguish.remove(s.charAt(j));
				
					startIndex = temp + 1;
				}
				distinguish.put(s.charAt(i), i);
				max = Math.max(max, i - startIndex + 1);
			}
		}
		return max;    
    }
}

　　

Code 2:

public class Solution {
    public int lengthOfLongestSubstring(String s) {
        int len = 0;
        HashSet<Character> hset = new HashSet<Character>(); 
        if(s.length() > 0){
            StringBuffer temp = new StringBuffer();
            temp.append(s.charAt(0));
            hset.add(s.charAt(0));
            ++len;
            for(int i = 1; i < s.length(); ++i){
                if(hset.contains(s.charAt(i))){
                    StringBuffer abf = new StringBuffer();
                    abf.append(s.charAt(i));                    
                    int index = temp.indexOf(abf.toString());
                    temp.delete(0, index + 1);
                }
                else
                    hset.add(s.charAt(i));                
                temp.append(s.charAt(i));
                if(temp.length() > len)
                    len = temp.length();
            }            
        }
        return len;
    }
}