Description
Given a string s, return the length of the longest substring between two equal characters, excluding the two characters. If there is no such substring return -1.
A substring is a contiguous sequence of characters within a string.
Example 1:
Input: s = "aa"
Output: 0
Explanation: The optimal substring here is an empty substring between the two 'a's.
Example 2:
Input: s = "abca"
Output: 2
Explanation: The optimal substring here is "bc".
Example 3:
Input: s = "cbzxy"
Output: -1
Explanation: There are no characters that appear twice in s.
Example 4:
Input: s = "cabbac"
Output: 4
Explanation: The optimal substring here is "abba". Other non-optimal substrings include "bb" and "".
Constraints:
- 1 <= s.length <= 300
- s contains only lowercase English letters.
分析
题目的意思是：移除两个相同字符串后剩下子串的最大长度，很显然分别移除位于最左的相同字符串就可以了。因此用一个字典保存字符串最左边的位置，当遍历到相同的字符串维护更新最大长度res就行了。
代码
class Solution:
def maxLengthBetweenEqualCharacters(self, s: str) -> int:
d={}
res=-1
for i in range(len(s)):
if(s[i] in d):
res=max(res,i-d[s[i]]-1)
else:
d[s[i]]=i
return res
参考文献
[LeetCode] 3 Solutions | Naive | Two Pass | One Pass O(n)