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fn main() {
let s = "abcda".to_string();
dbg!(Solution::longest_palindrome(s));
}
struct Solution(());
impl Solution {
pub fn longest_palindrome(s: String) -> String {
use std::collections::HashMap;
if s.len() == 1 {
return s;
}
let s = s.chars().collect::<Vec<char>>();
if s.len() == 2 {
if s[0] != s[1] {
return s[0].to_string();
} else {
return s.into_iter().collect::<String>();
}
}
let mut hm: HashMap<char, Vec<usize>> = HashMap::new();
let mut ls = s[0].to_string();
for (idx, c) in s.iter().enumerate() {
if let Some(indices) = hm.get(&c) {
for c_idx in indices.iter() {
let ss = &s[*c_idx..=idx];
if Self::is_palindrome(ss) && ss.len() > ls.len() {
ls = ss.clone().into_iter().collect::<String>();
}
}
hm.entry(*c)
.and_modify(|v| v.push(idx));
} else {
hm.insert(c.clone(), vec![idx]);
}
}
ls
}
pub fn is_palindrome(slice: &[char]) -> bool {
if slice.len() == 2 {
return &slice[0] == &slice[1];
}
let mut l = 0;
let mut r = slice.len() - 1;
while l < r {
if slice[l] != slice[r] {
return false;
}
l += 1;
r -= 1;
}
return true;
}
}
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