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Given a string s, find the length of the longest substring without repeating characters.

 

Example 1:

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.

Example 2:

Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Example 3:

Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.

Example 4:

Input: s = ""
Output: 0

 

Constraints:

  • 0 <= s.length <= 5 * 104
  • s consists of English letters, digits, symbols and spaces.

public int lengthOfLongestSubstring(String s) { int i=0; int j=0; int max = 0; HashSet<Character> set = new HashSet<Character>(); while(j<s.length() && i<s.length()){ char sc = s.charAt(i); char ec = s.charAt(j); if(set.contains(ec)){ set.remove(sc); i++; } else{ set.add(ec); max = Math.max(max, set.size()); j++; } } return max; }

The basic idea of solving this problem is to keep track of all the characters we have already visited and maintain a window size in which each character appeared only once. So throughout the traversal whenever the window size is maximum, that will give us the result.

 

Time Complexity: O(n)  // For traversing all the items in the array.

Space Complexity: O(n) // for keeping track of already visited items in the window, in the worst case all items will be present in the HashSet.


Execution:


Input: