Longest Substring Without Repeating Characters

题目

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

Example 1:

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.

Example 2:

Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Example 3:

Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.

Constraints:

• 0 <= s.length <= 5 * 104
• s consists of English letters, digits, symbols and spaces.

我的解答

class Solution {
    public int lengthOfLongestSubstring(String s) {
        if (s == null || s.length() == 0) {
            return 0;
        }
        int length = s.length();

        // 记录字符串的最大位置 下标是ascii , 值是位置
        int [] arr = new int[128];
        Arrays.fill(arr,-1);

        // 窗口边界
        int left = 0;

        int max = 0;
        for (int i = 0; i < length; i++) {
            int ascii = s.charAt(i);
            if(arr[ascii] >= left ){
                // 有重复的，左边边界往前推到重复的下一位
                left = arr[ascii]+1;
            }else{
                // 没有就用当前的刷新一下最大长度
                max = Math.max(max,i-left + 1);
            }
            // 记录最大的位置
            arr[ascii] = i ;
        }
        return max;
    }
}

链接：https://leetcode.cn/problems/longest-substring-without-repeating-characters