寻找最长不重复子串

寻找最长不重复子串

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(时间复杂度为O(n))

1. 遍历字符串，过程中将出现过的字符存入字典，key为字符，value为字符下标

2. 用maxLength保存遍历过程中找到的最大不重复子串的长度

3. 用start保存最长子串的开始下标

4. 如果字符已经出现在字典中，更新start的值

5. 如果字符不在字典中，更新maxLength的值

6. return maxLength

代码

class Solution(object):
    def lengthOfLongestSubstring(self, s):
        """
        :type s: str
        :rtype: int
        """
        start = maxLength = 0
        usedChar = {}

        for i in range(len(s)):
            if s[i] in usedChar and start <= usedChar[s[i]]:
                start = usedChar[s[i]] + 1
            else:
                maxLength = max(maxLength, i - start + 1)
            usedChar[s[i]] = i

        return maxLength

本题以及其它leetcode题目代码github地址: github地址