D116 409. Longest Palindrome

Topic link

409. Longest Palindrome

Subject analysis

Returns the longest palindrome string length that can be formed from a given string.

Train of thought

Count the number of occurrences with array_count_values. And distinguish between even and odd occurrences of the letter. Array_sum is a straightforward way to count the number of letters that occur even times. For an odd number of letters, only one can be included in the middle of the palindrome string. So we have to subtract n minus 1 from the sum. Where n is the number of letters with odd occurrences.

The final code

      
class Solution {

    / * * *@param String $s
     * @return Integer
     */
    function longestPalindrome($s) {
        $s = str_split($s);
        $amounts = array_count_values($s);
        $total = 0;
        $maxOdd = 0;
        foreach($amounts as $v){
            $total += $v;
            if($v%2! =0){
                $total -=1;
                if($v > $maxOdd){ $maxOdd = $v; }}}if($maxOdd! =0){
            $total+=1;
        }
        return$total; }}Copy the code

This scenario beat only 15.8% of the code. Subsequently, the following programme was used:

      
class Solution {

    / * * *@param String $s
     * @return Integer
     */
    function longestPalindrome($s) {
        $s = str_split($s);
        $amounts = array_count_values($s);
        $odd = [];
        $even = [];
        array_walk($amounts, function($v, $k) use (&$odd, &$even){
            if($v%2! =0){
                $odd[$k] = $v;
            }
            else{ $even[$k] = $v; }}); $odds = count($odd);if(!empty($odds)){
            $odds--;
        }
        $total = array_sum($even) + array_sum($odd) - $odds;
        return$total; }}Copy the code

You beat 100%. Call it a day!

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