LeetCode 3. Longest Substring Without Repeating Characters 原创Java参考解答
问题描述
https://leetcode.com/problems/longest-substring-without-repeating-characters/
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.
解题思路
题目是求字符串中最长的无重复字符串的长度。
快慢指针O(N)解法:快指针j、慢指针i。
快指针 j 检查 j 位置字符是否在在HashSet中
- 不在的话,就继续向右移动 j 指针, 并更新最大长度。
- 若在的话,则删除HashSet头部字符,即 i 所在位置字符,并移动 i 指针。
参考代码
public class Solution { public int lengthOfLongestSubstring(String s) { int i = 0; int j = 0; int longest = 0; HashSet<Character> set = new HashSet<>(); while (j < s.length()) { if (!set.contains(s.charAt(j))) { set.add(s.charAt(j++)); longest = Math.max(longest, set.size()); } else { set.remove(s.charAt(i++)); } } return longest; } }