Strings

Question 1

3. Longest Substring Without Repeating Characters

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

Answer 1

Base concept: sliding window

1. Initialize hash set
2. Initialize left pointer
3. Initialize max length var to return
4. Create for loop in range of length of s with pointer r
5. Create nested while loop that checks if current char(using index r) is in hash set
6. Keep removing from chars from the hash set, iterating from through s with index of left pointer (incrementing by 1) until the current value is no longer found
7. Add the current value to hash set
8. Find max by taking max of max length var and (r - l + 1)

Question 2

424. Longest Repeating Character Replacement

Answer 2

https://leetcode.com/problems/longest-repeating-character-replacement/

Question 3

242. Valid Anagram

Answer 3

https://leetcode.com/problems/valid-anagram/

Question 4

49. Group Anagrams

Answer 4

https://leetcode.com/problems/group-anagrams/

Question 5

20. Valid Parentheses

Answer 5

https://leetcode.com/problems/valid-parentheses/

Question 6

125. Valid Palindrome

Answer 6

https://leetcode.com/problems/valid-palindrome/

Question 7

5. Longest Palindromic Substring

Answer 7

https://leetcode.com/problems/longest-palindromic-substring/

Question 8

647. Palindromic Substrings

Answer 8

https://leetcode.com/problems/palindromic-substrings/