leetcode 3. Longest Substring Without Repeating Characters (java)

class Solution {
    public int lengthOfLongestSubstring(String s) {
        int[] dict = new int[256];
        Arrays.fill(dict, -1);
        int maxLen = 0, start = -1;
        for (int i = 0; i < s.length(); i++) {
            if (dict[s.charAt(i)] > start) {
                start = dict[s.charAt(i)];
            }
            dict[s.charAt(i)] = i;
            maxLen = Math.max(maxLen, i - start);
        }
        return maxLen;
    }
}

//时间复杂度: O(n)
//空间复杂度: O(1)