LongestSubstringWitoutRepeats.java

package two_pointers;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

/**
 * Created by gouthamvidyapradhan on 09/03/2017.
 Given a string, find the length of the longest substring without repeating characters.

 Examples:

 Given "abcabcbb", the answer is "abc", which the length is 3.

 Given "bbbbb", the answer is "b", with the length of 1.

 Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence and not a substring.
 */
public class LongestSubstringWitoutRepeats
{
    Set<Character> set = new HashSet<>();
    /**
     * Main method
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception
    {
        System.out.println(new LongestSubstringWitoutRepeats().lengthOfLongestSubstring("asdfsdfsdfsdfasdfdjdjjdjjdjjjjjajsdjjdjdjjd"));
    }

    private int lengthOfLongestSubstring(String s)
    {
        if(s == null || s.isEmpty()) return 0;
        Map<Character, Integer> map = new HashMap<>();
        int i = 0, max = Integer.MIN_VALUE;
        for(int j = 0, l = s.length(); j < l; j ++)
        {
            if(map.keySet().contains(s.charAt(j)))
            {
                i = Math.max(map.get(s.charAt(j)) + 1, i);
            }
            map.put(s.charAt(j), j);
            max = Math.max(max, (j - i) + 1);
        }
        return max;
    }
}