leetcode3:不重复的最长子串长度

package hashmap;

import java.util.HashMap;
import java.util.Map;

public class hashmap {

 public static void main(String[] args) {
  String s="dvdf";
        if(s==null||s.length()==0){
            System.out.println("null");
        }
        int result=1;
        Map<Character,Integer> charIndexMap= new HashMap<>();
        int[] length = new int[s.length()];
        int lastDuplicate = 0;
        length[0]=1;
        charIndexMap.put(s.charAt(0),0);

        for(int i=1;i<s.length();i++){
            Character ch = s.charAt(i);
            if(charIndexMap.containsKey(ch)){
                length[i]=i-Math.max(charIndexMap.get(s.charAt(i)),lastDuplicate);
                lastDuplicate = Math.max(lastDuplicate, charIndexMap.get(s.charAt(i)));
            }
            else{
                length[i]=length[i-1]+1;
            }
            charIndexMap.put(ch,i);
            result = Math.max(result,length[i]);
        }
       System.out.println(result);

 }

}