LeetCode(3) Longest Substring Without Repeating Characters解题报告

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本文介绍LeetCode第3题：求给定字符串中最长的无重复字符子串的长度。通过滑动窗口的方式遍历字符串，使用HashSet记录当前子串包含的字符，当遇到重复字符时调整窗口范围。

LeetCode(3) Longest Substring Without Repeating Characters

问题:

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

大意:

求字符串最长没有重复字符的子串的长度。

示例:

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.

解题方案:

这道思路比较简单，下面列举一个比较容易想到的解题思路。

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