3. Longest Substring Without Repeating Characters (python)

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.

Constraints:

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

class Solution(object):
    def lengthOfLongestSubstring(self, s):
        """
        :type s: str
        :rtype: int
        """
        i = 0
        j = 0
        d = {}
        ans = 0
        while j < len(s):
            if s[j] not in d or i > d[s[j]]:
                ans = max(ans, j - i + 1)
                d[s[j]] = j
            else:
                i = d[s[j]] + 1
                ans = max(ans, j - i + 1)
                j -= 1
            j += 1
        
        return ans