Sum vs XOR

HackerRank 問題: Sum vs XOR
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Question

Given an integer n , find each x such that:

  • 0 <= x <= n
  • n + x = n ^ x

where ^ denotes the bitwise XOR operator. Return the number of x's satisfying the criteria.

HackerRank 問題: Sum vs XOR

Answer

<?php

/*
 * Complete the 'sumXor' function below.
 *
 * The function is expected to return a LONG_INTEGER.
 * The function accepts LONG_INTEGER n as parameter.
 */

function sumXor($number) {
    $sum_xor_number = 1;

    if ($number == 0) {
        return 1;
    }
    // transform number to binary number
    $binary_number = decbin($number);
    $binary_number_array = str_split($binary_number);

    // search each binary number
    foreach ($binary_number_array as $binary_code) {
        if ($binary_code == 0) {
            // when binary code is 0, then could be the sum xor number
            $sum_xor_number*=2;
        }
    }

    return $sum_xor_number;
}

$fptr = fopen(getenv("OUTPUT_PATH"), "w");

$n = intval(trim(fgets(STDIN)));

$result = sumXor($n);

fwrite($fptr, $result . "\n");

fclose($fptr);

Reference