0003: Longest Substring Without Repeating Characters

Problem Statement

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

Example 1:

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.

Example 2:

Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Example 3:

Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.

Constraints:

  • 0 <= s.length <= 5 * 104
  • s consists of English letters, digits, symbols and spaces.

Code Solution

class Solution:
    def lengthOfLongestSubstring(self, s):
		
        lx = 0
        cmax = 0
        
        cache = {}
        for rx, c in enumerate(s):
	        
			# only look in current window:
            if c in cache and cache[c] >= lx:
                lx = cache[c] + 1
            
            cache[c] = rx
            cmax = max(cmax, rx - lx + 1)
        
        return cmax