# 3. Longest Substring Without Repeating Characters

Longest Substring Without Repeating Characters - LeetCode

Given a string s, find the length of the longest substring without repeating 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
``````class Solution:
def lengthOfLongestSubstring(self, s: str) -> int:
res = 0
sub = []
for i,v in enumerate(s):
if v not in sub:
sub.append(v)
res = max(res, len(sub))
else:
cur_v_i = sub.index(v)
sub = sub[cur_v_i+1:]
sub.append(v)
return res

``````
• code #slidingwindow
``````class Solution:
# @return an integer
def lengthOfLongestSubstring(self, s):
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

``````