lintcode 中等题：longest substring without repeating characters 最长无重复字符的子串

public class Solution {
    /**
     * @param s: a string
     * @return: an integer 
     */
    public int lengthOfLongestSubstring(String s) {
        // write your code here
        HashMap<Character,Integer> map = new HashMap<Character,Integer>();
        if(s == null)
            return 0;
        if(s.length() <=1)
            return s.length();
        int longest = -1;
        for(int i = 0;i<s.length();i++){
            char ch = s.charAt(i);
            if(map.containsKey(ch)){
                longest = Math.max(map.size(),longest);
                i = map.get(ch);
                map.clear();
            }else{
                map.put(ch,i);
            }
        }
        longest = Math.max(map.size(),longest);
        map.clear();
        return longest;
    }
}