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.
public class Solution {
public int MaxLengthBetweenEqualCharacters(string s) {
var map = new Dictionary<char,int>();
var maxLen = -1;
for(int i=0;i<s.Length;i++){
if(map.ContainsKey(s[i])){
int diff = i - map[s[i]];
if(diff-1 > maxLen){
maxLen = diff-1;
}
}
else{
map.Add(s[i],i);
}
}
return maxLen;
}
}Time Complexity: O(n)
Space Complexity: O(n)
