PHP Exercises: Memoize a given function results in memory

Last update on May 30 2022 11:47:03 (UTC/GMT +8 hours)

PHP: Exercise-99 with Solution

Write a PHP program to memoize a given function results in memory.

Note: In computing, memoization or memoisation is an optimization technique used primarily to speed up computer programs by storing the results of expensive function calls and returning the cached result when the same inputs occur again.

Sample Solution: -

PHP Code:

<?php
//Licence: https://bit.ly/2CFA5XY
function memoize($func)
{
    return function () use ($func) {
        static $cache = [];

        $args = func_get_args();
        $key = serialize($args);
        $cached = true;

        if (!isset($cache[$key])) {
            $cache[$key] = $func(...$args);
            $cached = false;
        }

        return ['result' => $cache[$key], 'cached' => $cached];
    };
}

$memoizedAdd = memoize(
    function ($num) {
        return $num + 10;
    }
);

var_dump($memoizedAdd(5));  
var_dump($memoizedAdd(6));  
var_dump($memoizedAdd(5));  
?>

Sample Output:

array(2) {
  ["result"]=>
  int(15)
  ["cached"]=>
  bool(false)
}
array(2) {
  ["result"]=>
  int(16)
  ["cached"]=>
  bool(false)
}
array(2) {
  ["result"]=>
  int(15)
  ["cached"]=>
  bool(true)
}

Flowchart:

PHP Code Editor:

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PHP: Tips of the Day

How to Sort Multi-dimensional Array by Value?

Try a usort, If you are still on PHP 5.2 or earlier, you'll have to define a sorting function first:

Example:

function sortByOrder($a, $b) {
    return $a['order'] - $b['order'];
}

usort($myArray, 'sortByOrder');

Starting in PHP 5.3, you can use an anonymous function:

usort($myArray, function($a, $b) {
    return $a['order'] - $b['order'];
});

And finally with PHP 7 you can use the spaceship operator:

usort($myArray, function($a, $b) {
    return $a['order'] <=> $b['order'];
});

To extend this to multi-dimensional sorting, reference the second/third sorting elements if the first is zero - best explained below. You can also use this for sorting on sub-elements.

usort($myArray, function($a, $b) {
    $retval = $a['order'] <=> $b['order'];
    if ($retval == 0) {
        $retval = $a['suborder'] <=> $b['suborder'];
        if ($retval == 0) {
            $retval = $a['details']['subsuborder'] <=> $b['details']['subsuborder'];
        }
    }
    return $retval;
});

If you need to retain key associations, use uasort() - see comparison of array sorting functions in the manual

Ref : https://bit.ly/3i77vCC