# LeetCode - 0003. Longest Substring Without Repeating Characters
### 題目網址：https://leetcode.com/problems/longest-substring-without-repeating-characters/
###### tags: `LeetCode` `Medium` `動態規劃（Dynamic Programming）`

/*
    -LeetCode format-
    Problem: 3. Longest Substring Without Repeating Characters
    Difficulty: Medium
    
    by Inversionpeter
*/



int lastAppearance[128];

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int longest = 0, nowStartAt = 0;
        memset(lastAppearance, -1, sizeof(lastAppearance));
        for (int i = 0; i != s.size(); ++i) {
            if (lastAppearance[s[i]] >= nowStartAt) {
                longest = max(longest, i - nowStartAt);
                nowStartAt = lastAppearance[s[i]] + 1;
            }
            lastAppearance[s[i]] = i;
        }
        return max(longest, int(s.size()) - nowStartAt);
    }
};