【剑指Offer】48. 最长不含重复字符的子字符串

class Solution {
    public int lengthOfLongestSubstring(String s) {
        int res = 0, left = 0;
        HashMap<Character, Integer> hash = new HashMap<>();
        for(int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if(hash.containsKey(c)) {
                left = Math.max(left, hash.get(c) + 1);
            }
            hash.put(c, i);
            res = Math.max(res, i - left + 1);
        }
        return res;
    }
}