# 1624. Largest Substring Between Two Equal Characters

## 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.


Constraints:

• 1 <= s.length <= 300
• s contains only lowercase English letters.

## Solutions

• class Solution {
public int maxLengthBetweenEqualCharacters(String s) {
int[] d = new int[26];
Arrays.fill(d, -1);
int ans = -1;
for (int i = 0; i < s.length(); ++i) {
int j = s.charAt(i) - 'a';
if (d[j] == -1) {
d[j] = i;
} else {
ans = Math.max(ans, i - d[j] - 1);
}
}
return ans;
}
}

• class Solution {
public:
int maxLengthBetweenEqualCharacters(string s) {
vector<int> d(26, -1);
int ans = -1;
for (int i = 0; i < s.size(); ++i) {
int j = s[i] - 'a';
if (d[j] == -1) {
d[j] = i;
} else {
ans = max(ans, i - d[j] - 1);
}
}
return ans;
}
};

• class Solution:
def maxLengthBetweenEqualCharacters(self, s: str) -> int:
d = {}
ans = -1
for i, c in enumerate(s):
if c in d:
ans = max(ans, i - d[c] - 1)
else:
d[c] = i
return ans


• func maxLengthBetweenEqualCharacters(s string) int {
d := make([]int, 26)
for i := range d {
d[i] = -1
}
ans := -1
for i, c := range s {
c -= 'a'
if d[c] == -1 {
d[c] = i
} else {
ans = max(ans, i-d[c]-1)
}
}
return ans
}

• function maxLengthBetweenEqualCharacters(s: string): number {
const n = s.length;
const pos = new Array(26).fill(-1);
let res = -1;
for (let i = 0; i < n; i++) {
const j = s[i].charCodeAt(0) - 'a'.charCodeAt(0);
if (pos[j] === -1) {
pos[j] = i;
} else {
res = Math.max(res, i - pos[j] - 1);
}
}
return res;
}


• impl Solution {
pub fn max_length_between_equal_characters(s: String) -> i32 {
let s = s.as_bytes();
let n = s.len();
let mut pos = [-1; 26];
let mut res = -1;
for i in 0..n {
let j = (s[i] - b'a') as usize;
let i = i as i32;
if pos[j] == -1 {
pos[j] = i;
} else {
res = res.max(i - pos[j] - 1);
}
}
res
}
}