Question

Consider I have this array:

$array = array(

'word1',
'abc',
'abc',
'word2',
 [other words]
'word1',
'dfg'
'word2',
 [other words]
);

I need to find the minimum distance between 2 given words. (let ‘word1’ and ‘word2’ be these 2 words)

In this case the minium distance between word1 and word2 is 1 because in the second group of words they are separated by only ‘dfg’.

I wrote a simple code but it’s too expsensive and I am looking for a faster version.

//> PSEUDO CODE
function minDistance( $words, $word1, $word2 ) {
    foreach( $words as $k=>$v) 
      if ( $v == $words1 )
         $positionsOfFirstWord[] = $k;

      if ( $v == $words2 )
         $positionsOfSecondWord[] = $k;


     //> If word1 or word2 was not found in the array then
     //> return max distance possibile (count($words))

     //> Now we have 2 array containg the position of both word we need.

     foreach( $positionsOfFirstWord as $v )
        foreach( $positionsOfSecondWord as $vv )
          $distance = abs($vv-$v);

}

Note the order of words in $array isn’t important (that’s why there is abs())

Do you think there could be a better version?

Please note the function must return 1 in this case too:

array(
 [other words]
'word2',
'dfg',
'word1'
 [other words]
);

Answer 1

I think a simple loop is enough. Keep track over the current minimum and of the last word1 and update current minimum if a word2 is found. Basically you are utilizing the fact that a word2 will always be closest to the last word1 found

 let minimum = INFINITY
 let lastword1 = -1
 let lastword2 =  -1
 foreach word w in words
 {

      if ( w is word1 )
      {
           lastword1 = current position;

           find distance between lastword2 and w update minimum if needed
      }

      if ( w is word2 )
      {
          lastword2 = current position;

          find distance between lastword1 and w update minimum if needed
      }

 }

You can do this in O(n) but there might faster ways if pre processing can be done and you need to answer multiple queries