LeetCode 409. Longest Palindrome

[quinnwencn]

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 here.

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.

[quinnwencn]

Analisys

Solution written in Cpp

#pragma once 
#include <string>
#include <array>

class Solution {
public:
    int longestPalindrome(std::string s) {
        std::array<uint16_t, 100> chars {0};
        for (auto c: s) {
            chars[c - 'A']++;
        }

        uint16_t count {0};
        bool onceFlag {true};
        for (auto i: chars) {
            if ((i > 1) && (i % 2 == 0)) {
                count += i;
            } else {
                count += i > 0 ? i-1 : 0;
            }

            if (onceFlag && i % 2 == 1) {
                count++;
                onceFlag = false;
            }
        }

        return count;
    }
};

Solution written in Rust

impl Solution {
    pub fn longest_palindrome(s: String) -> i32 {
        let mut chars = [0; 100];
        s.chars().for_each(|c| { chars[c as usize - 'A' as usize] += 1; });
        
        let mut count = 0;
        let mut once = true;
        for i in chars {
            if i % 2 == 0 {
                count += i;
            } else if i % 2 == 1 {
                count += i - 1;
                if once {
                    count += 1;
                    once = false;
                }
            }
        }

        count
    }
}

[quinnwencn]

https://review.gerrithub.io/c/robertwenhk/program-record/+/1193579