LeetCode 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 subsequenceand not a substring.

解法1： 参考自LeetCode题解3：Longest Substring Without Repeating Characters

class Solution:
    def lengthOfLongestSubstring(self, s):
        """
        :type s: str
        :rtype: int
        """
        start=0
        max_length=0
        n=len(s)
        sub_str=''
        for end in range(n):
            if s[end] not in sub_str:
                sub_str+=s[end]
            else:
                max_length=max(max_length,len(sub_str))
                while s[start]!=s[end]:
                    start+=1
                start+=1
                sub_str=s[start:end+1]
        return max(max_length,len(sub_str))

解法2： 参考自LeetCode该题目提交中 sample 64 ms submission

class Solution:
    def lengthOfLongestSubstring(self, s):
        """
        :type s: str
        :rtype: int
        """
        chars = {}
        begin = 0
        result = 0
        for i, c in enumerate(s, 1):
            if (c in chars) and (chars[c] > begin):
                begin = chars[c]
            elif (i - begin > result):
                result = i - begin              
            chars[c] = i
        return result