Longest Substring Without Repeating Characters

Posted 2020-08-04 鱼与海洋

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.

HashMap

public class Solution {
    public int lengthOfLongestSubstring(String s) {
      int max = 0;
      int start = 0;
      int end = 0;
      if(s.isEmpty()){
          return 0;
      }
      max = 1;
      HashMap<Character, Integer> map = new HashMap<Character, Integer>();
      char stringArray[] = s.toCharArray();
      while(end < s.length()){
          if(map.containsKey(stringArray[end])){
              if((end - start) > max)
                max = end - start ;
              if(map.get(stringArray[end]) >= start)
                start = map.get(stringArray[end]) + 1 ;
          }
          map.put(stringArray[end], end);
          end++;
      }
      return Math.max(max, end - start);
    }
}