3. Longest Substring Without Repeating Characters

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.

Similar: 159. Longest Substring with At Most Two Distinct Characters

 

public class Solution {
    public int lengthOfLongestSubstring(String s) {
        HashMap<Character, Integer> map = new HashMap<Character, Integer>();
        int max = 0;
        int start=0;
        for (int i = 0; i < s.length(); i++) {
            max = max > (i - start) ? max : (i-start); // [start,i), i is not included
            char c = s.charAt(i);
            if (map.containsKey(c)) {
                int j = map.get(c);
                while (start <= j) {
                    map.remove(s.charAt(start));
                    start++;
                }
            }
            map.put(c, i);
        }
        max = max > (s.length() - start) ? max : (s.length()-start); // As length = [start,i), i is not included
        return max;
    }
}