How to determine two numbers that are closer together in an array

Question

I have this array:

$arr = array (20, 1, 5, 10, 7, 16);

I would like to receive 5and 7. Because they are closer to each other than other objects. In other words, the difference between them is the smallest number:

7 - 5 = 2 // 2 is lowest number as the difference between all array items

How can i do this?

---

$keep = $arr[0];
$diff = $arr[1] - $arr[0];
foreach ($arr as $item) {
    if ( ($keep - $item) < $diff && $keep != $item ) {
        $diff = $item;
    }
}

My code is incomplete because it just compares the first element with other elements.

Answer 1

Explanation

So, to get the two numbers in the array that are closest to each other, you need to compare each value with the value of the other. But you do not need to compare them with yourself and with the previous ones that you have already compared.

, , :

(n)            n!
(k)   →   ─────────────
          k! * (n - k)!

_{n - k,}

:

n = 6 //Array elements
k = 2 //Two values which you compare

     6!                  720
─────────────   →   ─────────────   = 15 comparison
2! * (6 - 2)!          2  *  24

20 , 1 , 5 , 10 , 7 , 16  //Array values
↓    ↑   ↑   ↑    ↑   ↑
└────┴───┴───┴────┴───┘  //20 compared to all values, except itself
     ↓   ↑   ↑    ↑   ↑
     └───┴───┴────┴───┘  //1  compared to all values, except itself + [20]
         ↓   ↑    ↑   ↑
         └───┴────┴───┘  //5  compared to all values, except itself + [20, 1]
             ↓    ↑   ↑
             └────┴───┘  //10 compared to all values, except itself + [20, 1, 5]
                  ↓   ↑
                  └───┘  //7  compared to all values, except itself + [20, 1, 5, 10]

                         //16 compared to all values, except itself + [20, 1, 5, 10, 7]

, , 2 , . , , , 2 + 1.

for($key = 0, $length = count($arr); $key < $length; $key++){          
    for($innerKey = $key + 1; $innerKey < $length; $innerKey++){
      //↑ Skipping the previous values and the value itself    
    }               
}

. , , abs(), .

, , , , $nearest. ( $nearest + 1):

if( ($diff = abs($arr[$keys[$key]] - $arr[$keys[$innerKey]])) < $nearest)          

, , :

$result = [$arr[$keys[$key]], $arr[$keys[$innerKey]]];
$nearest = $diff;

<?php

    $arr = [20, 1, 5, 10, 7, 16];

    $keys = array_keys($arr);
    $nearest = max($arr) - min($arr) + 1;
    $result = [];

    for($key = 0, $length = count($arr); $key < $length; $key++){

        for($innerKey = $key + 1; $innerKey < $length; $innerKey++){

            if( ($diff = abs($arr[$keys[$key]] - $arr[$keys[$innerKey]])) < $nearest){
                $result = [$arr[$keys[$key]], $arr[$keys[$innerKey]]];
                $nearest = $diff;

            }

        }

    }

    print_r($result);

?>

[5, 7]

Answer 2

PHP usort , , quicksort.

$temp == >            $temp = [arr[$i] , arr[$j] , arr[$i]-arr[$j] ]

   $arr = array (20, 1, 5, 10, 7, 16);
   $temp=array();      
   for ($i = 0; $i < count($arr)-1; $i++)   
    {
        $diff=0;
        for ($j = $i+1; ($j < count($arr) && $i!=$j); $j++)
        {
            $diff=abs($arr[$i]-$arr[$j]);     //finding difference &taking absolute 
            $temp[] = array($arr[$i],$arr[$j], $diff); 
        }
    }
    usort($temp,function ($a, $b) { return $b[2] < $a[2]; });//sort `$temp[]` in ascending order according to the difference value
    list($x,$y,$d) = $temp[0];   //the first row of `$temp` contains values with the diff. is lowest 
                                //and the values is stored to `$x` & `$y` and there difference in `$d`
    echo "Related Values are $x and $y by $d"; 

http://ideone.com/pZ329m

 20  1    5  10   7  16          //inner loop -----------------------                      
 |   |    |   |   |   |  $temp[]=[[20,1,19],[20,5,15],[20,10,10],...//$i=0 |// `20` is compared values from 1 onwards and the values and differences are stored in `$temp[]`
 |___|____|___|___|___|  //(eg., $temp=[20,1,|20-1|])        //$j=1,2,3,4,5↓
     |    |   |   |   |          [1,5,4],[1,10,9],...               //$i=1 | `1` is compared with values from 5 onwards
     |____|___|___|___|                                     //$j=2,3,4,5   ↓outer loop
          |   |   |   |          [5,10,5],[5,7,2],...               //$i=2 | `5` is compared with values from 10 onwards
          |___|___|___|                                     //$j=3,4,5     ↓
              |   |   |          [10,7,3],[10,16,6]                 //$i=3 | `10` is compared with values from 7 onwards
              |___|___|                                     //$j=4,5       ↓
                  |   |          [7,16,9]]                          //$i=4 |`7` is compared with final value `16`
                  |___|                                     //$j=5         ↓

$temp[] differences.
$temp[] .

$temp[]

 Array
(
    [0] => Array
        (
            [0] => 7
            [1] => 5
            [2] => 2
        )

    [1] => Array
        (
            [0] => 7
            [1] => 10
            [2] => 3
        )

    [2] => Array
        (
            [0] => 16
            [1] => 20
            [2] => 4
        )

    [3] => Array
        (
            [0] => 5
            [1] => 1
            [2] => 4
        )

    [4] => Array
        (
            [0] => 10
            [1] => 5
            [2] => 5
        )

    [5] => Array
        (
            [0] => 16
            [1] => 10
            [2] => 6
        )

    [6] => Array
        (
            [0] => 7
            [1] => 1
            [2] => 6
        )

    [7] => Array
        (
            [0] => 16
            [1] => 7
            [2] => 9
        )

    [8] => Array
        (
            [0] => 10
            [1] => 1
            [2] => 9
        )

    [9] => Array
        (
            [0] => 10
            [1] => 20
            [2] => 10
        )

    [10] => Array
        (
            [0] => 16
            [1] => 5
            [2] => 11
        )

    [11] => Array
        (
            [0] => 7
            [1] => 20
            [2] => 13
        )

    [12] => Array
        (
            [0] => 5
            [1] => 20
            [2] => 15
        )

    [13] => Array
        (
            [0] => 16
            [1] => 1
            [2] => 15
        )

    [14] => Array
        (
            [0] => 1
            [1] => 20
            [2] => 19
        )

)

Answer 3

2 , . .

$arr = array (20, 1, 5, 10, 7, 16);

$c = count($arr);
$ld = max($arr);
for($i = 0; $i < $c; $i++){
    for($j = $i+1; $j < $c; $j++){
        $abs = abs($arr[$i]-$arr[$j]);
        if($abs < $ld)
            $ld = $abs;
    }
}
echo $ld; //2

, , , if.

Answer 4

$arr = array(20, 1, 5, 10, 7, 16);

$min = max($arr);
$closest = array();
foreach ($arr as $i) {
  foreach ($arr as $j) {
    if ($i != $j) {
      $diff = abs($i - $j);
      if ($min > $diff) {
        $min = $diff;
        $closest[0] = $i;
        $closest[1] = $j;
      }
    }
  }
}

print "The two closest numbers are " . $closest[0] . " and " . $closest[1];

Answer 5

, ... ,

//$arr = array (20, 1, 5, 10, 7, 16); gives 5 and 7
$arr = array (-32,-15,4,6,-14,613,4,63,6,4);
$diff = INF;
foreach ($arr as $item0) {
    foreach ($arr as $item1) {
        $localdiff = abs($item0 - $item1);
        if ( $localdiff > 0 && $localdiff < $diff ) {
            $diff = $localdiff;
            $keep0 = $item0;
            $keep1 = $item1;
        }
    }
}

echo "Smallest distance was $diff, between $keep0 and $keep1";

http://ideone.com/WdWOcb

Answer 6

 $arr = array (20, 1, 5, 10, 7, 16);

$temp = array();
foreach ($arr as $item1) {
    foreach ($arr as $item2) {
        $aV = abs($item1-$item2);
        if(!in_array($aV, $temp) && $aV!=0)
            $temp[$item1."-".$item2] =$aV;
    }   

}
$closest = array_keys($temp,min($temp));
list($first,$explode,$second) = $closest[0];
print "The two closest numbers are " . $first . " and " . $second;

Answer 7

, :

$arr = array( 14, 20, 1, 5, 10, 7, 16 );

2 (7-5, 16-14). .

( , , , +1), , , , ; , , :

$result = array( 'sum' => INF, 'values'=> array() );
for( $i=0; $i < count( $arr )-1; $i++ )
{
    for( $j = $i+1; $j < count( $arr ); $j++ )
    {
        $dif = abs( $arr[$i] - $arr[$j] );
        if( $dif < $result['sum'] )
        {
            $result = array( 'sum' => $dif, 'values'=> array( array( $arr[$i], $arr[$j] ) ) );
        }
        elseif( $dif == $result['sum'] )
        {
            $result['values'][] = array( $arr[$i], $arr[$j] );
        }
    }
}

, , :

Array
(
    [sum] => 2
    [values] => Array
        (
            [0] => Array
                (
                    [0] => 14
                    [1] => 16
                )
            [1] => Array
                (
                    [0] => 5
                    [1] => 7
                )
        )
)

, $result['values']. , (..) (5 7), usort -it:

usort( $result['values'], function( $a, $b ) { return min($a)-min($b); } );

$result['values'][0]:

[0] => Array
    (
        [0] => 5
        [1] => 7
    )

Answer 8

$arr = array (20, 1, 5, 10, 7, 16);
 arsort($arr, SORT_NUMERIC);
 $arr = array_values( $arr ); 
 $min = 0;
 foreach( $arr as $index => $number ){
   if( isset($arr[$index+1]) ){
     $diff = abs( $number - $arr[$index+1] );
      if( $diff < $min || $min == 0 ){
      $min = $diff;
      $result = array( $number, $arr[$index+1] );
     }
   }     
 }
 print_r( $result );