3. Longest Substring Without Repeating Characters

难度: Medium

题目描述

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

 

Example 1:

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3. Note that "bca" and "cab" are also correct answers.

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.

解题思路

代码实现

解决方案

java

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

        Set<Character> windowChars = new HashSet<>();
        int left = 0;
        int maxLen = 0;
        char[] chars = s.toCharArray();

        for (int right = 0; right < s.length(); right++) {
            while (windowChars.contains(chars[right])) {
                windowChars.remove(chars[left++]);
            }
            windowChars.add(chars[right]);
            maxLen = Math.max(maxLen, right - left + 1);
        }
        return maxLen;
    }

}