LeetCode 3. Longest Substring Without Repeating Characters-优快云博客

本文链接：https://blog.youkuaiyun.com/master5512/article/details/79117028

本文介绍了一种高效解决LeetCode上最长无重复字符子串问题的方法。通过使用滑动窗口技巧，实现了O(n)的时间复杂度，提供两种不同实现思路的代码示例。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

leetCode 3. Longest Substring Without Repeating Characters

Description

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

Examples:

Given “abcabcbb”, the answer is “abc”, which the length is 3.

Given “bbbbb”, the answer is “b”, with the length of 1.

Given “pwwkew”, the answer is “wke”, with the length of 3. Note that the answer must be a substring, “pwke” is a subsequence and not a substring.

    class Solution {
        public int lengthOfLongestSubstring(String s) {
            int n = s.length();
            Set<Character> set = new HashSet<>();
            int ans = 0, i = 0, j = 0;
            while (i < n && j < n) {
                if (!set.contains(s.charAt(j))) {
                    set.add(s.charAt(j++));
                    ans = Math.max(ans, j - i);
                }
                else {
                    set.remove(s.charAt(i++));
                }
            }
            return ans;
        }
    }

    public class Solution {
    public int lengthOfLongestSubstring(String s) {
        int n = s.length(), ans = 0;
        int[] index = new int[128]; // current index of character
        // try to extend the range [i, j]
        for (int j = 0, i = 0; j < n; j++) {
            i = Math.max(index[s.charAt(j)], i);
            ans = Math.max(ans, j - i + 1);
            index[s.charAt(j)] = j + 1;
        }
        return ans;
    }
}