Longest Substring Without Repeating Characters - LeetCode : Swift

Longest Substring Without Repeating Characters - LeetCode

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.

Constraints:

• 0 <= s.length <= 5 * 10^4
• s consists of English letters, digits, symbols and spaces.

Solution

class Solution {
    func lengthOfLongestSubstring(_ ar: String) -> Int {
        let ar = Array(ar)
        var low = 0, set: Set<Character> = [], count = 0
     
     for i in 0..<ar.count {
         if !set.contains(ar[i]) {
             set.insert(ar[i])
         } else {
             while ar[low] != ar[i] {
                set.remove(ar[low])
                 low += 1
             }
             low += 1
         }
         count = max(count, i - low + 1)
     }
     
     return count
    }
}