leetcode 3 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.

思路：滑动窗口和查找表；

题目要求的事 最长的不重复的子串；返回出长度；

这时候需要一个滑动窗口；然后再构建一个查找边查找新的元素是否已经存在；

CODE：：

class Solution {
public:
    int lengthOfLongestSubstring(string s)
    {
        int n=s.size();
        int left=0;
        int right=-1;//滑动窗口  [left,right];
        int freq[256]={0};//用来表示记录重复字符串的字典；
        int res=0;
        
        while(left<n)
        {
            if(right+1<n&&freq[s[right+1]]==0)
                freq[s[++right]]++;
            else 
                freq[s[left++]]--;//一直循环直到 去除重复 的那个点；
            res=max(res,right-left+1);
        }
        return res;
    }
};