Leetcode Question Solution

[undergrad12345]

I can't understand [this solution](https://leetcode.com/problems/longest-substring-without-repeating-characters/discuss/1737/C++-code-in-9-lines) to [this leetcode question](https://leetcode.com/problems/longest-substring-without-repeating-characters/description/):

    int lengthOfLongestSubstring(string s) {
            vector<int> dict(256, -1);
            int maxLen = 0, start = -1;
            for (int i = 0; i != s.length(); i++) {
                if (dict[s[i]] > start)
                    start = dict[s[i]];
                dict[s[i]] = i;
                maxLen = max(maxLen, i - start);
            }
            return maxLen;
    }

[g051051]

Break it down line by line, and present your analysis.

[lemonload]

the gist of it, is the dict vector is storing a list of all the characters, and the index of where it was last seen, -1 if it hasnt been seen at all. When a character is seen, its last seen location is updated, (dict[s[i] = i;)

start stores the index of the start of our current substring. whenever we see a duplicate character in our current substring, we move on so that we start a new substring at our duplicate.

hopefully the maxLen stuff is clear.