[LeetCode] Longest Substring Without Repeating Characters

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

 

Example 1:

Input: s = "abcabcbb" Output: 3 Explanation: The answer is "abc", with the length of 3.

Example 2:

Input: s = "bbbbb" Output: 1 Explanation: The answer is "b", with the length of 1.

Example 3:

Input: s = "pwwkew" Output: 3 Explanation: The answer is "wke", with the length of 3. Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.

Example 4:

Input: s = "" Output: 0

 

Constraints:

• 0 <= s.length <= 5 * 104
• s consists of English letters, digits, symbols and spaces.

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int ans = 0;
        unordered_map<char, int> unord;
        for (int i = 0, j = 0; j < s.length(); j++)
        {
            if (unord.find(s[j]) != unord.end())
            {
                i = max(unord[s[j]], i);
            }
            
            ans = max(ans, j - i + 1);
            unord[s[j]] = j + 1;
        }
        return ans;
    }
};