Description Link to heading

3.longest-substring-withou-repeating-characters

Solution Link to heading

We use arr[96] to record the number of occurence of each character. If the number is larger than 1, than there is repeating character between l and r; else, update res, if current length of substr is larger than res.

Code Link to heading 

class Solution {
  public:
    int lengthOfLongestSubstring(string s) {
        int arr[96] = {0};
        int res = 0;
        int l = 0;
        for (int r = 0; r < s.size(); r++) {
            arr[s[r] - ' ']++;
            if (arr[s[r] - ' '] > 1) {
                while (l < r && arr[s[r] - ' '] > 1)
                    arr[s[l++] - ' ']--;
            } else {
                res = max(r - l + 1, res);
            }
        }
        return res;
    }
};