Leetcode---3. Longest Substring Without Repeating Characters

Posted 2020-11-20 Hugh

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

Examples:

Given "abcabcbb", the answer is "abc", which the length is 3.

Given "bbbbb", the answer is "b", with the length of 1.

Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence and not a substring.

 

class Solution {
    public int lengthOfLongestSubstring(String s) {
        int max_length = 0;
        int left = 0;
        int right = 0;
        Set<Character> set = new HashSet<>();
        while(right < s.length()) {
            if(!set.contains(s.charAt(right))) {
                set.add(s.charAt(right++));
                max_length = Math.max(max_length, set.size());
            } else {
                set.remove(s.charAt(left++));
            }
        }
        return max_length;
    }
}