longest-substring-without-repeating-characters

Longest Substring Without Repeating Characters

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

Example 1:

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

Example 2:

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

Example 3:

Input: "pwwkew"
Output: 3
Explanation: 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.

Complexity Analysis (HashMap approach):

• Time complexity : O(n). We sweep through the list once

• Space complexity : O(n). The size of the hashmap can be all the elements in the whole array if they are unique

Complexity Analysis (HashSet approach):

• Time complexity : O(2n) = O(n). In the worst case each character will be visited twice by left_pointer and right_pointer.

• Space complexity : O(n). The size of the hashset can be all the elements in the whole array if they are unique

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