LeetCode第3题 Longest Substring Without Repeating Character(c++)

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

Example 1:

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.
Example 2:

Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.
Example 3:

Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.
Example 4:

Input: s = ""
Output: 0
 

Constraints:

0 <= s.length <= 5 * 104
s consists of English letters, digits, symbols and spaces.

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/longest-substring-without-repeating-characters
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题目大意：

返回无重复字母的最大子串的长度。

实现思路：

利用双指针，并将每个元素存入set中，利用set.count()来查看是否存在重复字母，并进行相应的指针移动。

实现代码：

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        set st;
        int n=s.length();
        int l=0,r=0;
        int ans=0;
        for(int i=0;i