import java.util.HashMap; import java.util.Map; /* * Given a string, find the length of the longest substring without repeating characters. Example 1: Input: "abcabcbb" Output: 3 Explanation: The answer is "abc", with the length of 3. Example 2: Input: "bbbbb" Output: 1 Explanation: The answer is "b", with the length of 1. Example 3: Input: "pwwkew" Output: 3 Explanation: 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. */ public class Lc3 { // ·滑动窗口 public static int lengthOfLongestSubstring(String s) { // key 值 - 当前值,value 值-当前的位置 Map<Character, Integer> map = new HashMap<Character, Integer>(); int ans = 0; char[] ch = s.toCharArray(); for (int end = 0, start = 0; end < ch.length; end++) { // ·如果map包含当前值,更新其位置 if (map.containsKey(ch[end])) { start = Math.max(map.get(ch[end]), start); } // ·每次更新最大距离,当前位置减去上一次重复的位置,再往后加一位即是本次的最大距离 ans = Math.max(ans, end - start + 1); map.put(ch[end], end + 1); } return ans; } public static void main(String[] args) { String s = "dvdf"; System.out.println(lengthOfLongestSubstring(s)); } }