409. Longest Palindrome 🔗
Date: Jun 04, 2024
Tags: hash-table
Description
Given a string s
which consists of lowercase or
uppercase letters, return the length of the longest
palindrome that
can be built with those letters.
Letters are case sensitive, for example,
"Aa"
is not considered a palindrome.
Example 1:
Input: s = "abccccdd" Output: 7 Explanation: One longest palindrome that can be built is "dccaccd", whose length is 7.
Example 2:
Input: s = "a" Output: 1 Explanation: The longest palindrome that can be built is "a", whose length is 1.
Constraints:
-
1 <= s.length <= 2000
-
s
consists of lowercase and/or uppercase English letters only.
Optimal
function longestPalindrome(s: string): number {
const len = s.length;
if (len === 1) return 1;
if (len === 0) return 0;
let result = 0;
const hash = new Map();
for (let i = 0; i < len; i++) {
const char = s[i];
const prev = hash.get(char) ?? 0;
hash.set(char, prev + 1);
const current = hash.get(char);
if (current % 2 === 0) result += 2;
}
return result !== len ? result + 1 : result;
}
export { longestPalindrome };