剑指 Offer II 016. 不含重复字符的最长子字符串

class Solution {
    public int lengthOfLongestSubstring(String s) {
        // 不包含重复字符的
        if (s == null || s.length() == 0) return 0;
        char[] chars = s.toCharArray();
        Map<Character,Integer> windows = new HashMap<>();
        int left = 0, right = 0, maxLen = 0, len = s.length();
        while (right < len) {
            char add = chars[right++];
            // 放入map中
            windows.put(add, windows.getOrDefault(add, 0) + 1);
            while (windows.get(add) > 1) {
                char remove = chars[left++];
                // update 
                windows.put(remove, windows.get(remove) - 1);
            }
            // get maxLen
            maxLen = Math.max(maxLen, right - left);
        }
        return maxLen;
    }
}