Question

How to find the two elements in an array whose sum is closest to zero in PHP

Answer 1

function findClosestToZero($arr) {
    if (count($arr) < 2) {
        echo "arr must have at least two elements.\n";
        return;
    }

    // Step 1: Sort the arr
    $sortedArr = $arr;
    sort($sortedArr);

    $left = 0;
    $right = count($sortedArr) - 1;
    $closestSum = PHP_INT_MAX;
    $closestPair = [0, 0];

    // Step 2: Use two-indexed technique
    while ($left < $right) {
        $sum = $sortedArr[$left] + $sortedArr[$right];

        // Update closest sum and pair if needed
        if (abs($sum) < abs($closestSum)) {
            $closestSum = $sum;
            $closestPair[0] = $sortedArr[$left];
            $closestPair[1] = $sortedArr[$right];
        }

        // Move indexeds
        if ($sum < 0) {
            $left++; // Increase sum by moving left indexed
        } else {
            $right--; // Decrease sum by moving right indexed
        }
    }

    // Output the result
    echo "The two elements whose sum is closest to zero are: " .
         $closestPair[0] . " and " . $closestPair[1] .
         " with a sum of " . $closestSum . ".\n";
}

$arr = [23, -26, -88, -42, 55, 99, -11, 90, -13, 17, -31];

findClosestToZero($arr);



/*
run:

The two elements whose sum is closest to zero are: -88 and 90 with a sum of 2.

*/

 

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