Formatted question description: https://leetcode.ca/all/1624.html

1624. Largest Substring Between Two Equal Characters (Easy)

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.

Related Topics:
String

Solution 1.

// OJ: https://leetcode.com/problems/largest-substring-between-two-equal-characters/

// Time: O(N)
// Space: O(1)
class Solution {
public:
    int maxLengthBetweenEqualCharacters(string s) {
        int ans = -1;
        for (int i = 'a'; i <= 'z'; ++i) {
            int first = -1, last = -1;
            for (int j = 0; j < s.size(); ++j) {
                if (s[j] != i) continue;
                if (first == -1) first = j;
                last = j;
            }
            ans = max(ans, last - first - 1);
        }
        return ans;
    }
};

Java

class Solution {
    public int maxLengthBetweenEqualCharacters(String s) {
        int maxLength = -1;
        Map<Character, Integer> map = new HashMap<Character, Integer>();
        int length = s.length();
        for (int i = 0; i < length; i++) {
            char c = s.charAt(i);
            if (map.containsKey(c)) {
                int prevIndex = map.get(c);
                maxLength = Math.max(maxLength, i - prevIndex - 1);
            } else
                map.put(c, i);
        }
        return maxLength;
    }
}

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