Longest Substring Without Repeating Characters, longestrepeating

Longest Substring Without Repeating Characters, longestrepeating

Today, I started to record leetcode and write it in a simple way. Sorry.

Longest Substring Without Repeating Characters

Question:

Given a string, find the length of the longest substring without repeating characters.

Given a string, find its longest non-repeated substring

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"IsSubsequenceAnd not a substring.

 

I read a method on the Internet, which is very interesting. The time complexity is o (n). First, the parameter m is a list with a size of 256. You can store the corresponding location of each character in the string based on ascii.

Example: 'aab'-> m [97] = 0, m [65] = 1, m [98] = 2

Max res record length

Start is used to record the starting position of substring

When s [I] appears for the first time, m [ord (s [I])] = 0

Or s [I] appears multiple times, but when the starting position is greater than the previous location where the same character appears, res is updated.

Res = max (res, I-start + 1)

Otherwise, update the start position to the location where the same characters appear.

 

 1 class Solution(object): 2     def lengthOfLongestSubstring(self, s): 3         """ 4         :type s: str 5         :rtype: int 6         """ 7         m = [0]*256 8         res = 0 9         start = 010         for i in range(len(s)):11             c = ord(s[i])12             if (m[c] == 0 or m[c]<start):13                 res = max(res,i+1-start)14             else:15                 start = m[c]16             m[c] = i+117         return res

References:

[LeetCode] Longest Substring Without Repeating Characters