[Leetcode]3. Longest Substring Without Repeating Characters @python

题目

Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for “abcabcbb” is “abc”, which the length is 3. For “bbbbb” the longest substring is “b”, with the length of 1.

题目要求

给定一个字符串，找到这个字符串中最长的没有重复字符的子串的大小

解题思路

利用两个指针，一个指向子字符串的开头，一个指向子字符串的结尾，两个指针之间不允许出现重复字符，利用哈希表存储已经出现过的字符，以及该字符出现的位置，向右移动右指针，如果当前指向的字符出现在子字符串当中，则将左指针指向子字符串中这个字符出现位置的下一个位置。

代码

class Solution(object):
def lengthOfLongestSubstring(self, s):
"""
:type s: str
:rtype: int
"""
left = right = 0
maxCount = 0
count = 0
hashtable = {}
while right < len(s):
if s[right] in hashtable and hashtable[s[right]] >= left:
maxCount = maxCount if maxCount >= (right - left) else (right - left)
left = hashtable[s[right]] + 1
hashtable[s[right]] = right
right += 1
maxCount = maxCount if maxCount >= right - left else right - left

return maxCount