3. Longest Substring Without Repeating Characters

Given a string s, find the length of the longest substring without repeating characters.

• new solution update 2022.02.14

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int arr[128]{false};
        int res = 0;
        for(int l=0, r = 0; r < s.length(); r++) {
            while(arr[s[r]]) {
                arr[s[l++]]--;
            }
            arr[s[r]]++;
            res = max(res, r - l + 1);
        }
        return res;
    }
};

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int result = 0;
        int current = 1;
        bool isChecked[128] = {false};
        int head = 0, tail = 0;

        for(tail = 0; tail < s.length(); tail++, current++) {
            if(isChecked[s[tail]]) {
                while(s[head] != s[tail]) {
                    isChecked[s[head++]] = false;
                    current--;
                }
                head++;
                current--;
            } else {
                isChecked[s[tail]] = true;
            }
            if(result < current)
                result = current;
        }

        return result;
    }
};