[Leetcode] 3. 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.

提交了无数次，最后终于过了，唉。。。。

用一个字典记录字符出现的位置。 用滑动窗口的思想，[i,j]区间保证是无重复子串，j往后加。如果s[j]已经在字典中记录过，位置为j'，则i往后滑至j‘+1处，依然j往后滑直至等于字符串长度n。

class Solution(object):
def lengthOfLongestSubstring(self, s):
"""
:type s: str
:rtype: int
"""

n = len(s)
d = dict()
i,j = 0,0
ans = 0

while i<n and j<n:
if d.has_key(s[j]):
i = max(d[s[j]]+1,i)
ans = max(ans, j-i+1)
d[s[j]] = j
j += 1

return ans