Comparison of algorithm efficiency for searching specific elements in PHP arrays

PHP array element search algorithm efficiency comparison: linear search: efficiency in unordered array is O(n); binary search (ordered array): time complexity is O(log n); hash table: time complexity is always is O(1), regardless of array type.

Comparison of algorithm efficiency for finding specific elements in PHP arrays

Finding specific elements in an array is a common task in PHP. There are several algorithms available for this purpose. This article will compare the efficiency of the three most common algorithms:

1. Linear search

function linearSearch($arr, $target) {
  for ($i = 0; $i < count($arr); $i++) {
    if ($arr[$i] === $target) {
      return $i;
    }
  }

  return -1;
}

2. Binary search (array must be ordered)

function binarySearch($arr, $target) {
  $left = 0;
  $right = count($arr) - 1;

  while ($left <= $right) {
    $mid = floor(($left + $right) / 2);

    if ($arr[$mid] === $target) {
      return $mid;
    } else if ($arr[$mid] < $target) {
      $left = $mid + 1;
    } else {
      $right = $mid - 1;
    }
  }

  return -1;
}

3. Hash table

Hash table can significantly improve the search speed by using key-value pairs to store data.

function hashTableSearch($arr, $target) {
  $lookupTable = [];

  for ($i = 0; $i < count($arr); $i++) {
    $lookupTable[$arr[$i]] = true;
  }

  if (isset($lookupTable[$target])) {
    return true;
  } else {
    return false;
  }
}

Practical case

We used different array sizes for testing, unordered arrays and ordered arrays containing random elements. The results are as follows:

Binary search performs best in ordered arrays, with a time complexity of O(log n), while hash tables perform best in ordered arrays. Most efficient in all cases, time complexity is always O(1).

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