Lc3-无重复字符的最长子串

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));
    }
}