LeetCode / Longest Substring Without Repeating Characters

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class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        # Init vars
        result = 0
        char_dict = dict()

        # Find max char_dict
        index = 0
        while index < len(s):
            char = s[index]
            # If char not in char_dict, Add the char to char_dict
            if char not in char_dict:
                char_dict[char] = index
                if len(char_dict) > result:
                    result = len(char_dict)
                index = index + 1
            # If char in char_dict, remake char_dict from duplicated char index
            else:
                index = char_dict[char] + 1
                char_dict = dict()

        return result

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class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        # Init vars
        left_index = 0              # left index of the sliding window
        max_length = 0              # maximum length of the substring
        last_seen_index = dict()    # last seen index of the character
        
        for right_index, char in enumerate(s):
            # if the character was seen and is inside the current window
            if char in last_seen_index and last_seen_index[char] >= left_index:
                # move the left pointer to avoid duplicates
                left_index = last_seen_index[char] + 1
            
            # update the last seen index of this character
            last_seen_index[char] = right_index
            
            # update the maximum window size
            max_length = max(max_length, right_index - left_index + 1)
        
        return max_length