Longest Substring Without Repeating Characters - LeetCode

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

这道题不用太追求高深的算法，两层循环也是OK的。

public class Solution {
    public int lengthOfLongestSubstring(String s) {
        if (s == null || s.length() == 0) {
            return 0;
        }
        
        HashSet set = new HashSet();
        
        int leftBound = 0, max = 0;
        for (int i = 0; i < s.length(); i++) {
            if (set.contains(s.charAt(i))) {
                while (leftBound < i && s.charAt(leftBound) != s.charAt(i)) {
                    set.remove(s.charAt(leftBound));
                    leftBound ++;
                }
                leftBound ++;
            } else {
                set.add(s.charAt(i));
                max = Math.max(max, i - leftBound + 1);
            }
        }
        
        return max;
    }
}