Is the following array well defined for binary search?

Question

Hello,

I have a file with consisted of int;int values in each line. Both columns are ascending, row by row. I plan to load that file into an array with following code:

while( ! feof($f) ) {
    $line = fgets( $f, 32 );
    $tmp = explode( ";", $line );
    $elements[] = array( $tmp[0] => $tmp[1] );
}

I intend to use this array to do a binary search based on the key $tmp[0]. Array will have 1000 elements, but the search will be applied for 10.000 different values. Should I simply define a 2x1000 matrix and load elements into it?

Thx

Answer 1

You can use file to get the entire contents of a file as an array of lines. Assuming that the first int in each pair is unique, you can use it as the key for the array:

foreach (file('ints.txt') as $line) {
  list($key, $value) = explode(';', $line);
  $elements[$key] = $value;
}

Looking up values by their keys in $elements will be O(n) but really close to O(1); this might be fast enough for your purposes.