Given a string, find the length of the longest substring without repeating characters.
给定一个字符串，在不重复字符的情况下找出最长子字符串的长度
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.题目就是要求找出最长的无重复子串
可以采用滑动窗口的方法，用i和j分别指向窗口的前后下界，如果当前字符未出现在窗口，j后移，如果出现了，i后移。窗口用集合实现，判存复杂度为O(1)。总的时间复杂度为O(2n)=O(n)，最坏情况为每个字符都被访问两遍(分别作为窗口的头尾)，空间复杂度为O(k)
class Solution: def lengthOfLongestSubstring(self, s): L=len(s) if L==0: return 0 i=j=0 chardict=set() maxlen=0 while i<L and j<L: if s[j] not in chardict: chardict.add(s[j]) maxlen=max(maxlen,j-i+1) j+=1 else: chardict.remove(s[i]) i+=1 return maxlen if __name__=='__main__': s='abcabcbb' b=Solution().lengthOfLongestSubstring(s) print(b)