4055 Longest Balanced Substring I
Longest Balanced Substring I 
You are given a string s consisting of lowercase English letters.
A substring of s is called balanced if all distinct characters in the substring appear the same number of times.
Return the length of the longest balanced substring of s.
Example 1:
Input: s = “abbac”
Output: 4
Explanation:
The longest balanced substring is “abba” because both distinct characters ‘a’ and ‘b’ each appear exactly 2 times.
Example 2:
Input: s = “zzabccy”
Output: 4
Explanation:
The longest balanced substring is “zabc” because the distinct characters ‘z’, ‘a’, ‘b’, and ‘c’ each appear exactly 1 time.
Example 3:
Input: s = “aba”
Output: 2
Explanation:
One of the longest balanced substrings is “ab” because both distinct characters ‘a’ and ‘b’ each appear exactly 1 time. Another longest balanced substring is “ba”.
Constraints:
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1 <= s.length <= 1000
s consists of lowercase English letters.
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use std::collections::HashMap;
impl Solution {
pub fn longest_balanced(s: String) -> i32 {
// only 1000 as length
//all substrings in 10^ 6
let mut res = 0;
for (i,k1) in s.chars().enumerate() {
let mut hs: HashMap<char, i32> = HashMap::new();
for (j,k2) in s[i..].chars().enumerate() {
*hs.entry(k2).or_insert(0) += 1;
let mut a = 0;
let mut found = true;
for &count in hs.values() {
if a == 0 {
a = count;
} else if a != count {
found = false;
break;
}
}
if found {
res = res.max(j+ 1 );
}
}
}
return res as i32;
}
}