Find longest substring without repeating characters

Question

Given a string S of length N find longest substring without repeating characters.

Example:

Input:

Answer 1

Question: Find the longest substring without repeating characters. Example 1 :

    import java.util.LinkedHashMap;
    import java.util.Map;

    public class example1 {

        public static void main(String[] args) {
            String a = "abcabcbb";
               // output => 3
            System.out.println( lengthOfLongestSubstring(a));

        }

        private static int lengthOfLongestSubstring(String a) {
               if(a == null  || a.length() == 0) {return  0 ;}  
               int res = 0 ;
            Map map = new LinkedHashMap<>();
              for (int i = 0; i < a.length(); i++) {
                  char ch = a.charAt(i);
                if (!map.containsKey(ch)) {
       //If ch is not present in map, adding ch into map along with its position
                    map.put(ch, i);

                }else {
/*
If char ch is present in Map, reposition the cursor i to the position of ch and clear the Map.
*/ 
                    i = map.put(ch, i);// updation of index
                     map.clear();
                }//else

                res = Math.max(res, map.size());

            }



            return res;
        }

    }

if you want the longest string without the repeating characters as output then do this inside the for loop:

String res ="";// global
    int len = 0 ;//global
 if(len < map.size()) {
     len = map.size();
    res = map.keySet().toString();
 }
System.out.println("len -> " + len);
System.out.println("res => " + res);