LongestSubstringWitoutRepeats.java

/* (C) 2024 YourCompanyName */
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.
 *
 * <p>Examples:
 *
 * <p>Given "abcabcbb", the answer is "abc", which the length is 3.
 *
 * <p>Given "bbbbb", the answer is "b", with the length of 1.
 *
 * <p>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;
  }
}