Find nearest sum of numbers in array to a given number

问题

Say I have an array [10000,5000,1000,1000] and I would like to find the closest sum of numbers to a given number. Sorry for the bad explanation but here's an example:

Say I have an array [10000,5000,1000,1000] I want to find the closest numbers to, say 6000.

Then the method should return 5000 and 1000

another example : we want the closest to 14000 , so then he should return 10000 and 5000

here i've tried on php but it's something wrong when i put 6000 i should get 5000 and 1000

<?php

$arr    = [10000,5000,1000,1000];
$x      = 6000;
var_dump(eek($x,$arr));

function eek($x,$arr)
{
    $index = [];
    $counter = 0;
    foreach($arr as $val)
    {
        if($counter + $val <= $x)
        {
            $counter += $val;
            $index[] = $val;
        }
        elseif($counter + $val >= $x)
        {
            $counter += $val;
            $index[] = $val;
            break;
        }
    }

    if($counter == $x)
    {
        return $index;
    }
    elseif($counter >= $x)
    {
        return $index;    
    }
    else
    {
        return [];
    }
}

?>

Anyone have solution about it ?

回答1:

Here it is works with float and negative values:

$numbers = array(
    10000,5000,1000,1000
);
$desiredSum = 6000;
$minDist = null;
$minDist_I = null;
// Iterate on every possible combination
$maxI = pow(2,sizeof($numbers));
for($i=0;$i<$maxI;$i++) {
    if(!(($i+1) % 1000)) echo ".";

    // Figure out which numbers to select in this 
    $sum = 0;
    for($j=0;$j<sizeof($numbers);$j++) {
        if($i & (1 << $j)) {
            $sum += $numbers[$j];
        }
    }
    $diff = abs($sum - $desiredSum);
    if($minDist_I === null || $diff < $minDist) {
        $minDist_I = $i;
        $minDist = $diff;
    }

    if($diff == 0) break;
}
$chosen = array();
for($j=0;$j<sizeof($numbers);$j++) {
    if($minDist_I & (1 << $j)) $chosen[] = $numbers[$j];
}
echo "\nThese numbers sum to " . array_sum($chosen)  . " (closest to $desiredSum): ";
echo implode(", ", $chosen);
echo "\n";

回答2:

Taking in count that the array is ordered from bigger to smaller values

Here is a solution, starting from yours

function eek($x,$arr)
{
    $index = [];
    $counter = 0;
    foreach($arr as $key => $val) {
        if($counter + $val < $x) {
            $counter += $val;
            $index[] = $val;
        } else {
            if (isset($arr[$key+1]) && (abs($counter + $arr[$key+1] -$x) < abs($counter + $val -$x))) {
                continue;
            } else {
                $index[] = $val;
                return $index;
            }
        }
    }

    return $index;
}

来源：https://stackoverflow.com/questions/58918556/find-nearest-sum-of-numbers-in-array-to-a-given-number