Longest Substring Without Repeating Characters

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

Have you met this question in a real interview? 

Yes

Example

For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3.

For "bbbbb" the longest substring is "b", with the length of 1.

Challenge

O(n) time

public class Solution {
    /**
     * @param s: a string
     * @return: an integer
     */
    public int lengthOfLongestSubstring(String s) {
        // write your code here
        boolean[] record = new boolean[256];
        int maxLen = 0;
        int start = 0;
        for(int i = 0; i < s.length(); i++){
            char c = s.charAt(i);
            if(record[c]){
                maxLen = Math.max(maxLen, i - start);
                for(int j = start; j < i; j++){
                    if(c == s.charAt(j)){
                        start = j + 1;
                        break;
                    }
                    record[s.charAt(j)] = false;
                }
            }
            record[c] = true;
           
        }
        maxLen = Math.max(maxLen, s.length() - start);
        return maxLen;
    }
}