3. Longest Substring Without Repeating Characters（js）

给定一个字符串，请你找出其中不含有重复字符的 最长子串 的长度。

示例 1:

输入: "abcabcbb"
输出: 3
解释: 因为无重复字符的最长子串是 "abc"，所以其长度为 3。
示例 2:

输入: "bbbbb"
输出: 1
解释: 因为无重复字符的最长子串是 "b"，所以其长度为 1。
示例 3:

输入: "pwwkew"
输出: 3
解释: 因为无重复字符的最长子串是 "wke"，所以其长度为 3。
  请注意，你的答案必须是 子串 的长度，"pwke" 是一个子序列，不是子串。

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.

代码如下：

var lengthOfLongestSubstring = function(s) {
    var set=new Set();
    var max=0;
    var len=s.length,i=0,j=0;
   while(i<len){
       //如果没有重复，存入set
        if(!set.has(s.charAt(i))){
            set.add(s.charAt(i++));
            max=Math.max(max,set.size);
        }else{
        //有重复，删除头一个再比较
            set.delete(s.charAt(j++))
        }
    }
    return max;
};

 出处：https://leetcode-cn.com/problems/longest-substring-without-repeating-characters/

　　　https://leetcode.com/problems/longest-substring-without-repeating-characters/