3、不含重复字符的最长子串

实现方案1：

public int longestSubStr(String str) {
        int max = 0;
        Deque<Character> deque = new ArrayDeque<>();

        for (int i = 0; i < str.length(); i++) {
            if (!deque.contains(str.charAt(i))) {
                deque.addLast(str.charAt(i));
            } else {
                max = Math.max(max, deque.size());
                while (deque.peek() != str.charAt(i)) {
                    deque.removeFirst();
                }
                deque.removeFirst();
                deque.addLast(str.charAt(i));
            }
        }
        max = Math.max(max, deque.size());

        return max;
    }

实现方案2：

// 不含重复字符的最大子串
    public static int noRepeatStr(String s) {
       int maxLen = 0;
       int left = 0;

        Map<Character, Integer> map = new HashMap<>();

        for (int i = 0; i < s.length(); i++) {
            if (map.containsKey(s.charAt(i))) {
                left = Math.max(left, map.get(s.charAt(i)) + 1);
            }

            map.put(s.charAt(i), i);
            maxLen = Math.max(maxLen, i - left + 1);

        }

        return maxLen;
    }